Operators in php

1. Assignment operator
2. Arithmetic operator
3. Comparison operator
4. String operator
5. Increment operator
6. Logical operator ( Exclusive OR operation
1). Boolean value - String
2). String - Conversion of numbers
3). String - Conversion of Boolean value
4). Number - - Boolean value Conversion of
5). Conversion of numbers to strings

Control structure
1. if single-way branch
2. if /else double-way branch, the two code segments in if/else in the double-way branch, one and only one section must be executed

if/else if/else if.../else multi-way branch
3. switch case, which is convenient for comparing multiple possible values of the variable being judged.
4. while (expression){
code segment}
5. do{
code segment;}while(expression);
6. for(statement 1; statement 2; statement 3) {
code segment;}
Statement 1, execute first and only once
then judge statement 2, if true, execute the code segment; then execute statement 3;
then judge statement 2... loop
until Statement 2 is false, for ends
Code display
<span style="color: #008080;"> 1</span> <span style="color: #008000;">//</span><span style="color: #008000;">============================== =============
</span><span style="color: #008080;"> 2</span>
<span style="color: #008080;"> 3</span> <span style="color: #008000;">//2. Arithmetic operations </span>Return to original position
<span style="color: #008080;"> 4</span> <span style="color: #008000;">//
</span><span style="color: #008080;"> 5</span> <span style="color: #008000;">//How to add, subtract, multiply and divide in php program
</span><span style="color: #008080;"> 6</span> <span style="color: #008000;">//In order - </span>
<span style="color: #008080;"> 7</span>
<span style="color: #008080;"> 8</span>
<span style="color: #008080;"> 9</span> <span style="color: #800080;">$a</span> = 3<span style="color: #000000;">;
</span><span style="color: #008080;"> 10</span> <span style="color: #800080;">$b</span> =5<span style="color: #000000;">;
</span><span style="color: #008080;"> 11</span> <span style="color: #800080;">$c</span> = <span style="color: #800080;">$a</span> <span style="color: #800080;">$b</span>;<span style="color: #008000;">//</span><span style="color: #008000;">This sentence The meaning is that the calculation result of $a $b is assigned to $c</span>
<span style="color: #008080;"> 12</span> <span style="color: #0000ff;">echo</span> <span style="color: #800080;">$c</span>,'<br />'<span style="color: #000000;">;
</span><span style="color: #008080;"> 13</span> <span style="color: #0000ff;">echo</span> <span style="color: #800080;">$b</span>-<span style="color: #800080;">$a</span>,'<br />'<span style="color: #000000;">;
</span><span style="color: #008080;"> 14</span>
<span style="color: #008080;"> 15</span> <span style="color: #0000ff;">echo</span> <span style="color: #800080;">$a</span> * <span style="color: #800080;">$b</span>,'<br />';<span style="color: #008000;">//</span><span style="color: #008000;">Calculate the result of $a * $b and assign it to $c </span>
<span style="color: #008080;"> 16</span> <span style="color: #0000ff;">echo</span> <span style="color: #800080;">$b</span>/<span style="color: #800080;">$a</span>,'<br />';<span style="color: #008000;">//</span><span style="color: #008000;">Calculate the result of $b/$a and assign it to $c
</span><span style="color: #008080;"> 17</span>
<span style="color: #008080;"> 18</span> <span style="color: #008000;">//If it is in C language, $b and $a are both integer types, so the calculated $c is also an integer type
</span><span style="color: #008080;"> 19</span> <span style="color: #008000;">//In php, the value of a variable can be changed at will, and the type of the variable can also be changed.
</span><span style="color: #008080;"> 20</span> <span style="color: #008000;">//
</span><span style="color: #008080;"> 21</span> <span style="color: #008000;">//For example: variable $c is an integer, and you can suddenly assign it a floating-point value.
</span><span style="color: #008080;"> 22</span> <span style="color: #008000;">//So php is called a dynamic language.</span><span style="color: #008080;"> 23</span>
<span style="color: #008080;"> 24</span>
<span style="color: #008080;"> 25</span>
<span style="color: #008080;"> 26</span>
<span style="color: #008080;"> 27</span> <span style="color: #008000;">//----------------------------------------- ---------------</span>
<span style="color: #008080;"> 28</span> <span style="color: #000000;">Finding the remainder is to take the modulo operation and return to the original position
</span><span style="color: #008080;"> 29</span> <span style="color: #000000;">When calculating division on the computer, 2 results are calculated
</span><span style="color: #008080;"> 30</span>
<span style="color: #008080;"> 31</span> <span style="color: #000000;">Quotient and remainder
</span><span style="color: #008080;"> 32</span>
<span style="color: #008080;"> 33</span> */
<span style="color: #008080;"> 34</span> <span style="color: #800080;">$a</span> = 3<span style="color: #000000;">;
</span><span style="color: #008080;"> 35</span> <span style="color: #800080;">$b</span> = 5<span style="color: #000000;">;
</span><span style="color: #008080;"> 36</span> <span style="color: #800080;">$c</span> = <span style="color: #800080;">$b</span>%<span style="color: #800080;">$a</span>; <span style="color: #008000;">//</span><span style="color: #008000;"> gets 1 Yu 2</span>
<span style="color: #008080;"> 37</span> <span style="color: #0000ff;">echo</span> <span style="color: #800080;">$c</span>,'<br />'<span style="color: #000000;">;
</span><span style="color: #008080;"> 38</span>
<span style="color: #008080;"> 39</span>
<span style="color: #008080;"> 40</span> <span style="color: #008000;">//</span><span style="color: #008000;">Quick test to determine whether a number is even or odd?
</span><span style="color: #008080;"> 41</span> <span style="color: #008000;">//You can take modulo 2, the remainder is 1, then it is an odd number, if the remainder is 0, it is an odd number</span>
<span style="color: #008080;"> 42</span>
<span style="color: #008080;"> 43</span> <span style="color: #800080;">$d</span> = 3<span style="color: #000000;">;
</span><span style="color: #008080;"> 44</span> <span style="color: #800080;">$res</span> = <span style="color: #800080;">$d</span> % 2<span style="color: #000000;">;
</span><span style="color: #008080;"> 45</span> <span style="color: #0000ff;">if</span>(<span style="color: #800080;">$res</span> == 1<span style="color: #000000;">){
</span><span style="color: #008080;"> 46</span> <span style="color: #0000ff;">echo</span> <span style="color: #800080;">$d</span>,'is an odd number'<span style="color: #000000;">;
</span><span style="color: #008080;"> 47</span> <span style="color: #000000;">}
</span><span style="color: #008080;"> 48</span> <span style="color: #0000ff;">if</span>(<span style="color: #800080;">$res</span> == 0<span style="color: #000000;">){
</span><span style="color: #008080;"> 49</span> <span style="color: #0000ff;">echo</span> <span style="color: #800080;">$d</span>,'is an even number'<span style="color: #000000;">;
</span><span style="color: #008080;"> 50</span> <span style="color: #000000;">}</span><span style="color: #008080;"> 51</span>
<span style="color: #008080;"> 52</span> <span style="color: #008000;">//</span><span style="color: #008000;">I am in junior high school and have the concept of negative numbers</span>
<span style="color: #008080;"> 53</span>
<span style="color: #008080;"> 54</span> <span style="color: #800080;">$b</span> = -5<span style="color: #000000;">;
</span><span style="color: #008080;"> 55</span> <span style="color: #800080;">$a</span> = 3<span style="color: #000000;">;
</span><span style="color: #008080;"> 56</span> <span style="color: #0000ff;">echo</span> <span style="color: #800080;">$b</span>%<span style="color: #800080;">$a</span><span style="color: #000000;">;
</span><span style="color: #008080;"> 57</span> <span style="color: #800080;">$b</span> = -5<span style="color: #000000;">;
</span><span style="color: #008080;"> 58</span> <span style="color: #800080;">$a</span> = -3<span style="color: #000000;">;
</span><span style="color: #008080;"> 59</span> <span style="color: #0000ff;">echo</span> <span style="color: #800080;">$b</span>%<span style="color: #800080;">$a</span><span style="color: #000000;">;
</span><span style="color: #008080;"> 60</span>
<span style="color: #008080;"> 61</span> <span style="color: #008000;">//</span><span style="color: #008000;">Note: During the modulo operation,
</span><span style="color: #008080;"> 62</span> <span style="color: #008000;">//The positive or negative result of the operation depends on the sign of the dividend
</span><span style="color: #008080;"> 63</span> <span style="color: #008000;">//The sign of the result is consistent with the sign of the dividend
</span><span style="color: #008080;"> 64</span> <span style="color: #008000;">//==================================== =============
</span><span style="color: #008080;"> 65</span>
<span style="color: #008080;"> 66</span> <span style="color: #008000;"> // Comparison operator Return to original position
</span><span style="color: #008080;"> 67</span> <span style="color: #008000;">// > ,< ,<= ,>= ==,!= ,=== (not only the values are equal, but the types are also equal),!= =</span>
<span style="color: #008080;"> 68</span> <span style="color: #800080;">$a</span> = 3<span style="color: #000000;">;
</span><span style="color: #008080;"> 69</span> <span style="color: #800080;">$b</span> = 2<span style="color: #000000;">;
</span><span style="color: #008080;"> 70</span> <span style="color: #0000ff;">if</span>(3 > 2<span style="color: #000000;">){
</span><span style="color: #008080;"> 71</span> <span style="color: #0000ff;">echo</span> '3 is greater than 2','<br />'<span style="color: #000000;">;
</span><span style="color: #008080;"> 72</span> }<span style="color: #0000ff;">else</span><span style="color: #000000;">{
</span><span style="color: #008080;"> 73</span> <span style="color: #0000ff;">echo</span> '3 is not greater than 2','<br />'<span style="color: #000000;">;
</span><span style="color: #008080;"> 74</span> <span style="color: #000000;">}
</span><span style="color: #008080;"> 75</span>
<span style="color: #008080;"> 76</span> <span style="color: #0000ff;">if</span>(<span style="color: #800080;">$a</span> >= <span style="color: #800080;">$b</span>){ <span style="color: #008000;">//</span><span style="color: #008000;"> >= It means that $a is greater than $b, or $a is equal to $b, either of which is true, that is, the condition satisfies </span>
<span style="color: #008080;"> 77</span> <span style="color: #0000ff;">echo</span> '3 is greater than or equal to 2','<br />'<span style="color: #000000;">;
</span><span style="color: #008080;"> 78</span> }<span style="color: #0000ff;">else</span><span style="color: #000000;">{
</span><span style="color: #008080;"> 79</span> <span style="color: #0000ff;">echo</span> '3 is not greater than or equal to 2','<br />'<span style="color: #000000;">;
</span><span style="color: #008080;"> 80</span> <span style="color: #000000;">}
</span><span style="color: #008080;"> 81</span> <span style="color: #008000;">//</span><span style="color: #008000;">-------------------------------- ------------------</span>
<span style="color: #008080;"> 82</span>
<span style="color: #008080;"> 83</span> <span style="color: #800080;">$a</span> = 3<span style="color: #000000;">;
</span><span style="color: #008080;"> 84</span> <span style="color: #800080;">$b</span> = '3'<span style="color: #000000;">;
</span><span style="color: #008080;"> 85</span> <span style="color: #0000ff;">if</span>(<span style="color: #800080;">$a</span> === <span style="color: #800080;">$b</span><span style="color: #000000;">){
</span><span style="color: #008080;"> 86</span> <span style="color: #0000ff;">echo</span> <span style="color: #800080;">$a</span>,'all equal to',<span style="color: #800080;">$b</span>,'<br />'<span style="color: #000000;">;
</span><span style="color: #008080;"> 87</span> }<span style="color: #0000ff;">else</span><span style="color: #000000;">{
</span><span style="color: #008080;"> 88</span> <span style="color: #0000ff;">echo</span> <span style="color: #800080;">$a</span>,'not exactly equal',<span style="color: #800080;">$b</span>,'<br />'<span style="color: #000000;">;
</span><span style="color: #008080;"> 89</span> <span style="color: #000000;">}
</span><span style="color: #008080;"> 90</span>
<span style="color: #008080;"> 91</span> <span style="color: #008000;">//</span><span style="color: #008000;">================================ ==========</span>
<span style="color: #008080;"> 92</span>
<span style="color: #008080;"> 93</span> <span style="color: #800080;">$a</span> = 3<span style="color: #000000;">;
</span><span style="color: #008080;"> 94</span> <span style="color: #800080;">$b</span> = <span style="color: #0000ff;">true</span><span style="color: #000000;">;
</span><span style="color: #008080;"> 95</span> <span style="color: #0000ff;">if</span>(<span style="color: #800080;">$a</span> == <span style="color: #800080;">$b</span><span style="color: #000000;">){
</span><span style="color: #008080;"> 96</span> <span style="color: #0000ff;">echo</span> <span style="color: #800080;">$a</span>,'equal to',<span style="color: #800080;">$b</span>,'<br />'<span style="color: #000000;"> ;
</span><span style="color: #008080;"> 97</span> }<span style="color: #0000ff;">else</span><span style="color: #000000;">{
</span><span style="color: #008080;"> 98</span> <span style="color: #0000ff;">echo</span> <span style="color: #800080;">$a</span>,'not equal to',<span style="color: #800080;">$b</span>,'<br />'<span style="color: #000000;">;
</span><span style="color: #008080;"> 99</span> <span style="color: #000000;">}</span><span style="color: #008080;">100</span> <span style="color: #008000;">//</span><span style="color: #008000;">When comparing different types
</span><span style="color: #008080;">101</span> <span style="color: #008000;">//php program itself
</span><span style="color: #008080;">102</span> <span style="color: #008000;">//
</span><span style="color: #008080;">103</span> <span style="color: #008000;">//The variable will be converted into a consistent type and then compared
</span><span style="color: #008080;">104</span> <span style="color: #008000;">//
</span><span style="color: #008080;">105</span> <span style="color: #008000;">//Remember the following conversions to return to the original position
</span><span style="color: #008080;">106</span> <span style="color: #008000;">//1. Boolean value - string
</span><span style="color: #008080;">107</span> <span style="color: #008000;">///2. String - Number conversion
</span><span style="color: #008080;">108</span> <span style="color: #008000;">///3. String - Boolean value conversion
</span><span style="color: #008080;">109</span> <span style="color: #008000;">//4. Number - - Boolean value conversion
</span><span style="color: #008080;">110</span> <span style="color: #008000;">///5. Number - Conversion of string
</span><span style="color: #008080;">111</span> <span style="color: #008000;">//
</span><span style="color: #008080;">112</span> <span style="color: #008000;">//Take 5 == true comparison as an example
</span><span style="color: #008080;">113</span> <span style="color: #008000;">//Convert the integer type to Boolean type
</span><span style="color: #008080;">114</span> <span style="color: #008000;">//
</span><span style="color: #008080;">115</span> <span style="color: #008000;">//In fact, in some languages, there is no Boolean type at all, and 1 and 0 are used as true/false
</span><span style="color: #008080;">116</span> <span style="color: #008000;">//0 / 0.0 These two are converted to boolean type to false
</span><span style="color: #008080;">117</span> <span style="color: #008000;">//Everything else is true, and negative numbers are also true
</span><span style="color: #008080;">118</span>
<span style="color: #008080;">119</span>
<span style="color: #008080;">120</span>
<span style="color: #008080;">121</span>
<span style="color: #008080;">122</span> <span style="color: #008000;">//----------------------------------------- -----
</span><span style="color: #008080;">123</span> <span style="color: #008000;">//1. Boolean value - string </span>
<span style="color: #008080;">124</span> <span style="color: #0000ff;">true</span> ---'1'
<span style="color: #008080;">125</span> <span style="color: #0000ff;">false</span>--- ''
<span style="color: #008080;">126</span>
<span style="color: #008080;">127</span> <span style="color: #008000;">//</span><span style="color: #008000;">-------------------------------- ----------
</span><span style="color: #008080;">128</span> <span style="color: #008000;">//1. String - conversion of numbers
</span><span style="color: #008080;">129</span> <span style="color: #008000;">//Start looking for numbers from the left end of the string until the end of the first non-number. The part taken out is the converted value
</span><span style="color: #008080;">130</span> <span style="color: #008000;">//'3q'----3</span>
<span style="color: #008080;">131</span> '123asdf'---123
<span style="color: #008080;">132</span> 'sdfds789'----0
<span style="color: #008080;">133</span>
<span style="color: #008080;">134</span> <span style="color: #800080;">$num</span> = 'sdfds789'<span style="color: #000000;">;
</span><span style="color: #008080;">135</span> <span style="color: #0000ff;">echo</span> <span style="color: #800080;">$num</span> 0; <span style="color: #008000;">//</span><span style="color: #008000;">The result of the operation is 0
</span><span style="color: #008080;">136</span>
<span style="color: #008080;">137</span> <span style="color: #008000;">//----------------------------------------- -----
</span><span style="color: #008080;">138</span> <span style="color: #008000;">///3. String - Boolean conversion
</span><span style="color: #008080;">139</span> <span style="color: #008000;">//''String, '0', this is converted to false
</span><span style="color: #008080;">140</span> <span style="color: #008000;">//Everything else is true</span>
<span style="color: #008080;">141</span>
<span style="color: #008080;">142</span>
<span style="color: #008080;">143</span>
<span style="color: #008080;">144</span> <span style="color: #0000ff;">if</span>(''==<span style="color: #0000ff;">false</span><span style="color: #000000;">){
</span><span style="color: #008080;">145</span> <span style="color: #0000ff;">echo</span> 'Empty string equals false'<span style="color: #000000;">;
</span><span style="color: #008080;">146</span> }<span style="color: #0000ff;">else</span><span style="color: #000000;">{
</span><span style="color: #008080;">147</span> <span style="color: #0000ff;">echo</span> 'Empty string is not equal to false'<span style="color: #000000;">;
</span><span style="color: #008080;">148</span> <span style="color: #000000;">}
</span><span style="color: #008080;">149</span>
<span style="color: #008080;">150</span> <span style="color: #0000ff;">echo</span> '<br />'<span style="color: #000000;">;
</span><span style="color: #008080;">151</span> <span style="color: #0000ff;">if</span>('0'==<span style="color: #0000ff;">false</span><span style="color: #000000;">){
</span><span style="color: #008080;">152</span> <span style="color: #0000ff;">echo</span> 'String 0 equals false'<span style="color: #000000;">;
</span><span style="color: #008080;">153</span> }<span style="color: #0000ff;">else</span><span style="color: #000000;">{
</span><span style="color: #008080;">154</span> <span style="color: #0000ff;">echo</span> 'String 0 is not equal to false'<span style="color: #000000;">;
</span><span style="color: #008080;">155</span> <span style="color: #000000;">}</span><span style="color: #008080;">156</span>
<span style="color: #008080;">157</span>
<span style="color: #008080;">158</span> <span style="color: #008000;">//</span><span style="color: #008000;">-------------------------------- ----------
</span><span style="color: #008080;">159</span> <span style="color: #008000;">///4. String - Boolean conversion
</span><span style="color: #008080;">160</span> <span style="color: #008000;">// Only integer 0, and floating point 0.0, convert to false
</span><span style="color: #008080;">161</span> <span style="color: #008000;">//Others, even negative numbers, are converted to true
</span><span style="color: #008080;">162</span>
<span style="color: #008080;">163</span>
<span style="color: #008080;">164</span>
<span style="color: #008080;">165</span> <span style="color: #008000;">//----------------------------------------- -----
</span><span style="color: #008080;">166</span> <span style="color: #008000;">//5. Number - Conversion of string
</span><span style="color: #008080;">167</span> <span style="color: #008000;">//Directly the literal itself </span>
<span style="color: #008080;">168</span> <span style="color: #0000ff;">echo</span> '<br />'<span style="color: #000000;">;
</span><span style="color: #008080;">169</span> <span style="color: #0000ff;">echo</span> 'aaa'. 2323<span style="color: #000000;">;
</span><span style="color: #008080;">170</span>
<span style="color: #008080;">171</span>
<span style="color: #008080;">172</span>
<span style="color: #008080;">173</span> <span style="color: #008000;">//</span><span style="color: #008000;">-------------------------------- ----------
</span><span style="color: #008080;">174</span> <span style="color: #008000;">//String Return to original position
</span><span style="color: #008080;">175</span>
<span style="color: #008080;">176</span> <span style="color: #008000;">//In php strings, there is an operation, which is splicing (the difference between ',' and '.' in echo)</span>
<span style="color: #008080;">177</span>
<span style="color: #008080;">178</span> <span style="color: #800080;">$str1</span> = 'hello'<span style="color: #000000;">;
</span><span style="color: #008080;">179</span> <span style="color: #800080;">$str2</span> = ''<span style="color: #000000;">;
</span><span style="color: #008080;">180</span>
<span style="color: #008080;">181</span> <span style="color: #800080;">$str3</span> = 'world'<span style="color: #000000;">;
</span><span style="color: #008080;">182</span> <span style="color: #0000ff;">echo</span> <span style="color: #800080;">$str1</span>.<span style="color: #800080;">$str2</span>.<span style="color: #800080;">$str3</span><span style="color: #000000;">;
</span><span style="color: #008080;">183</span> <span style="color: #0000ff;">echo</span> <span style="color: #800080;">$str1</span>,<span style="color: #800080;">$str2</span>,<span style="color: #800080;">$str3</span><span style="color: #000000;">;
</span><span style="color: #008080;">184</span>
<span style="color: #008080;">185</span> <span style="color: #008000;">//</span><span style="color: #008000;"> Questions for newbies </span>
<span style="color: #008080;">186</span>
<span style="color: #008080;">187</span> <span style="color: #0000ff;">echo</span> <span style="color: #800080;">$str1</span>.<span style="color: #800080;">$str2</span>.<span style="color: #800080;">$str3</span><span style="color: #000000;">;
</span><span style="color: #008080;">188</span> <span style="color: #008000;">//</span><span style="color: #008000;">This line is the splicing operation of $str1, $str2, $str3 in memory
</span><span style="color: #008080;">189</span> <span style="color: #008000;">//Calculate a 'hello world' a large string,
</span><span style="color: #008080;">190</span> <span style="color: #008000;">//Then echo it to get the result of the judgment hello world
</span><span style="color: #008080;">191</span> <span style="color: #008000;">//==================================== =======</span>
<span style="color: #008080;">192</span>
<span style="color: #008080;">193</span> <span style="color: #0000ff;">echo</span> <span style="color: #800080;">$str1</span>,<span style="color: #800080;">$str2</span>,<span style="color: #800080;">$str3</span><span style="color: #000000;">;
</span><span style="color: #008080;">194</span> <span style="color: #008000;">//</span><span style="color: #008000;">echo is a statement, responsible for output
</span><span style="color: #008080;">195</span> <span style="color: #008000;">//You can use ',' to split and output multiple variables or values at once.
</span><span style="color: #008080;">196</span> <span style="color: #008000;">//
</span><span style="color: #008080;">197</span> <span style="color: #008000;">//To summarize:
</span><span style="color: #008080;">198</span> <span style="color: #008000;">//Use ' . ' to splice first and then output the whole
</span><span style="color: #008080;">199</span><span style="color: #008000;">//Use ' , ' to output the three variables one by one.</span><span style="color: #008080;">200</span> <span style="color: #008000;">//
</span><span style="color: #008080;">201</span> <span style="color: #008000;">//During the interview, you will encounter questions like:
</span><span style="color: #008080;">202</span> <span style="color: #008000;">//Use ' . ', use ' , ' which outputs quickly and efficiently
</span><span style="color: #008080;">203</span> <span style="color: #008000;">//
</span><span style="color: #008080;">204</span> <span style="color: #008000;">//Answer: Of course ',' The output is fast and the efficiency is high</span>
<span style="color: #008080;">206</span> <span style="color: #008000;">//======================================== ====
</span><span style="color: #008080;">207</span> <span style="color: #008000;">//The assignment operator is =. Its function is to assign the value on the right side of '=' to the variable on the left <span style="color: #008000;">Return to the original position</span></span>
<span style="color: #008080;">208</span> <span style="color: #800080;">$a</span> = 3<span style="color: #000000;">;
</span><span style="color: #008080;">209</span> <span style="color: #800080;">$b</span> = <span style="color: #800080;">$c</span> = 5<span style="color: #000000;">;
</span><span style="color: #008080;">210</span>
<span style="color: #008080;">211</span>
<span style="color: #008080;">212</span> <span style="color: #008000;">//</span><span style="color: #008000;">================================== ==========
</span><span style="color: #008080;">213</span> <span style="color: #008000;">//The result of the operator
</span><span style="color: #008080;">214</span> <span style="color: #008000;">//
</span><span style="color: #008080;">215</span> <span style="color: #008000;">//Everyone thinks: since it is an operation, after the operation is completed, there must be a result - the result value
</span><span style="color: #008080;">216</span> <span style="color: #008000;">//3 2; Operation result 5
</span><span style="color: #008080;">217</span> <span style="color: #008000;">//
</span><span style="color: #008080;">218</span> <span style="color: #008000;">//1. Comparison operator Return to original position
</span><span style="color: #008080;">219</span> <span style="color: #008000;">//Note: Comparing descriptors returns results, there are only 2 possibilities: true/false
</span><span style="color: #008080;">220</span> <span style="color: #008000;">//
</span><span style="color: #008080;">221</span> <span style="color: #008000;">//Take $a == $b as an example, either wait or not.
</span><span style="color: #008080;">222</span> <span style="color: #008000;">//It’s either true or false
</span><span style="color: #008080;">223</span> <span style="color: #008000;">//2 == 3; the operation result is: false
</span><span style="color: #008080;">224</span>
<span style="color: #008080;">225</span> <span style="color: #008000;">//======================================== ====
</span><span style="color: #008080;">226</span> <span style="color: #008000;">//2. String operator Return to original position
</span><span style="color: #008080;">227</span> <span style="color: #008000;">//String operator
</span><span style="color: #008080;">228</span> <span style="color: #008000;">//$a.$b
</span><span style="color: #008080;">229</span> <span style="color: #008000;">//Return result: spliced result
</span><span style="color: #008080;">230</span>
<span style="color: #008080;">231</span> <span style="color: #008000;">//======================================== ====
</span><span style="color: #008080;">232</span> <span style="color: #008000;">//Assignment operator, what is the return value?</span>
<span style="color: #008080;">233</span> <span style="color: #800080;">$a</span> = 3<span style="color: #000000;">;
</span><span style="color: #008080;">234</span> <span style="color: #0000ff;">if</span>(<span style="color: #800080;">$a</span> = 33<span style="color: #000000;">){
</span><span style="color: #008080;">235</span> <span style="color: #0000ff;">echo</span> 'aa'<span style="color: #000000;">;
</span><span style="color: #008080;">236</span> }<span style="color: #0000ff;">else</span><span style="color: #000000;">{
</span><span style="color: #008080;">237</span> <span style="color: #0000ff;">echo</span> 'bb'<span style="color: #000000;">;
</span><span style="color: #008080;">238</span> <span style="color: #000000;">}
</span><span style="color: #008080;">239</span> <span style="color: #008000;">//</span><span style="color: #008000;">The result of the long assignment operator is the value on the right side of = </span>
<span style="color: #008080;">240</span> <span style="color: #800080;">$a</span> = <span style="color: #800080;">$b</span> = <span style="color: #800080;">$c</span> =88
<span style="color: #008080;">241</span> <span style="color: #008000;">//</span><span style="color: #008000;">The process is like this, $b = 88 is performed first, and 88 is returned after assignment
</span><span style="color: #008080;">242</span> <span style="color: #008000;">//The returned 88 is assigned to $c
</span><span style="color: #008080;">243</span> <span style="color: #008000;">//Similarly…
</span><span style="color: #008080;">244</span> <span style="color: #008000;">//Finally $a is also assigned a value of 88
</span><span style="color: #008080;">245</span> <span style="color: #008000;">//
</span><span style="color: #008080;">246</span> <span style="color: #008000;">//
</span><span style="color: #008080;">247</span> <span style="color: #008000;">//Two difficulties;
</span><span style="color: #008080;">248</span> <span style="color: #008000;">//1. There is a type conversion problem during comparison operations
</span><span style="color: #008080;">249</span> <span style="color: #008000;">//2. Every operation must have a return value
</span><span style="color: #008080;">250</span> <span style="color: #008000;">//The comparison operation returns a Boolean value
</span><span style="color: #008080;">251</span> <span style="color: #008000;">//
</span><span style="color: #008080;">252</span> <span style="color: #008000;">//Assignment operation, returns the assigned value itself
</span><span style="color: #008080;">253</span>
<span style="color: #008080;">254</span> <span style="color: #008000;">//======================================== ====
</span><span style="color: #008080;">255</span> <span style="color: #008000;">//6. Logical operator Return to original position
</span><span style="color: #008080;">256</span> <span style="color: #008000;">//
</span><span style="color: #008080;">257</span> <span style="color: #008000;">//Proposition:
</span><span style="color: #008080;">258</span> <span style="color: #008000;">//True proposition, false proposition
</span><span style="color: #008080;">259</span> <span style="color: #008000;">//
</span><span style="color: #008080;">260</span> <span style="color: #008000;">//Logical operator: logical or || or
</span><span style="color: #008080;">261</span> <span style="color: #008000;">//Logical AND && and </span>
<span style="color: #008080;">262</span>
<span style="color: #008080;">263</span> <span style="color: #800080;">$house</span> = 180<span style="color: #000000;">;
</span><span style="color: #008080;">264</span> <span style="color: #800080;">$car</span> = 'BYD'<span style="color: #000000;">;
</span><span style="color: #008080;">265</span>
<span style="color: #008080;">266</span> <span style="color: #008000;">//</span><span style="color: #008000;">$res = $house && $car == 'BMW' If written like this, who will combine it first, which involves the issue of operation priority
</span><span style="color: #008080;">267</span> <span style="color: #008000;">//We recommend that when multiple quantities are to be moved, they need to be wrapped in a unit first and wrapped with ().For example: $res = $house && ($car == 'BMW')
</span><span style="color: #008080;">268</span> <span style="color: #008000;">//This can make the program easy to read and understand, and less likely to cause ambiguity </span>
<span style="color: #008080;">269</span> <span style="color: #0000ff;">if</span>(<span style="color: #800080;">$res</span> = <span style="color: #800080;">$house</span> && <span style="color: #800080;">$car</span> == 'BMW'<span style="color: #000000;">) {
</span><span style="color: #008080;">270</span> <span style="color: #0000ff;">echo</span> 'You can still marry'<span style="color: #000000;">;
</span><span style="color: #008080;">271</span> }<span style="color: #0000ff;">else</span><span style="color: #000000;">{
</span><span style="color: #008080;">272</span> <span style="color: #0000ff;">echo</span> 'Wait two more years'<span style="color: #000000;">;
</span><span style="color: #008080;">273</span> <span style="color: #000000;">}
</span><span style="color: #008080;">274</span>
<span style="color: #008080;">275</span> <span style="color: #000000;">Priority of logical operations
</span><span style="color: #008080;">276</span> && has a higher priority than ||<span style="color: #000000;">
</span><span style="color: #008080;">277</span> <span style="color: #000000;">But in development, it is not recommended to write them together and wrap them with application ()
</span><span style="color: #008080;">278</span> <span style="color: #800080;">$a</span> = 3<span style="color: #000000;">;
</span><span style="color: #008080;">279</span> <span style="color: #800080;">$b</span> = 5<span style="color: #000000;">;
</span><span style="color: #008080;">280</span> <span style="color: #0000ff;">if</span>((<span style="color: #800080;">$a</span>==8)||(<span style="color: #800080;">$b</span>=9<span style="color: #000000;">)){
</span><span style="color: #008080;">281</span> <span style="color: #800080;">$a</span> <span style="color: #000000;">;
</span><span style="color: #008080;">282</span> <span style="color: #800080;">$b</span> <span style="color: #000000;">;
</span><span style="color: #008080;">283</span> <span style="color: #000000;">}
</span><span style="color: #008080;">284</span> <span style="color: #0000ff;">echo</span> <span style="color: #800080;">$a</span>,'<br />',<span style="color: #800080;">$b</span><span style="color: #000000;">;
</span><span style="color: #008080;">285</span>
<span style="color: #008080;">286</span> <span style="color: #008000;">//</span><span style="color: #008000;">================================ ==========
</span><span style="color: #008080;">287</span>
<span style="color: #008080;">288</span> <span style="color: #008000;">//Logical inverse
</span><span style="color: #008080;">289</span> <span style="color: #008000;">//If a proposition is a true proposition, its counter-proposition is a false proposition
</span><span style="color: #008080;">290</span> <span style="color: #008000;">//Use ! to express </span><span style="color: #008080;">291</span>
<span style="color: #008080;">292</span> <span style="color: #008000;">//======================================== ====
</span><span style="color: #008080;">293</span> <span style="color: #008000;">//Exclusive OR operation xor returns to the original position
</span><span style="color: #008080;">294</span> <span style="color: #008000;">//XOR means that two conditions must be ‘one true’ and ‘one false’ to be true </span>
<span style="color: #008080;">295</span>
<span style="color: #008080;">296</span> <span style="color: #800080;">$li</span> = 'Male'<span style="color: #000000;">;
</span><span style="color: #008080;">297</span> <span style="color: #800080;">$mei</span> = 'Female'<span style="color: #000000;">;
</span><span style="color: #008080;">298</span> <span style="color: #008000;">//</span><span style="color: #008000;">What this XOR expresses is that one must be male, </span>
<span style="color: #008080;">299</span> <span style="color: #0000ff;">if</span>(<span style="color: #800080;">$li</span> == 'Male') xor (<span style="color: #800080;">$mei</span> == 'Male'<span style="color: #000000;">){
</span><span style="color: #008080;">300</span> <span style="color: #0000ff;">echo</span> 'Can get married'<span style="color: #000000;">;
</span><span style="color: #008080;">301</span> }<span style="color: #0000ff;">else</span><span style="color: #000000;">{
</span><span style="color: #008080;">302</span> <span style="color: #0000ff;">echo</span> 'Law prohibited, please go to Northern Europe'<span style="color: #000000;">;
</span><span style="color: #008080;">303</span> <span style="color: #000000;">}</span><span style="color: #008080;">304</span>
<span style="color: #008080;">305</span>
<span style="color: #008080;">306</span> <span style="color: #008000;">//</span><span style="color: #008000;">================================ ==========
</span><span style="color: #008080;">307</span> <span style="color: #008000;">//Ternary operator Return to original position
</span><span style="color: #008080;">308</span> <span style="color: #008000;">//
</span><span style="color: #008080;">309</span> <span style="color: #008000;">//Condition? Return value 1: Return value 2
</span><span style="color: #008080;">310</span> <span style="color: #008000;">//If the condition is true, return value 1, otherwise return value 2
</span><span style="color: #008080;">311</span> <span style="color: #008000;">//
</span><span style="color: #008080;">312</span> <span style="color: #008000;">//
</span><span style="color: #008080;">313</span> <span style="color: #008000;">//For example, determine whether a person is logged in on the website
</span><span style="color: #008080;">314</span> <span style="color: #008000;">//If logged in and the username is not empty, the username will be displayed
</span><span style="color: #008080;">315</span> <span style="color: #008000;">//If you are not logged in and the username is empty, the visitor will be displayed. .
</span><span style="color: #008080;">316</span>
<span style="color: #008080;">317</span> <span style="color: #008000;">//$user = 'zhangsan';
</span><span style="color: #008080;">318</span> <span style="color: #008000;">//if(!=''){
</span><span style="color: #008080;">319</span> <span style="color: #008000;">// echo $user;
</span><span style="color: #008080;">320</span> <span style="color: #008000;">//}else{
</span><span style="color: #008080;">321</span> <span style="color: #008000;">// echo 'visitor';
</span><span style="color: #008080;">322</span> <span style="color: #008000;">//}
</span><span style="color: #008080;">323</span> <span style="color: #008000;">//
</span><span style="color: #008080;">324</span> <span style="color: #008000;">//$user = 'zhangsan';
</span><span style="color: #008080;">325</span> <span style="color: #008000;">//echo $user?$user:'Visitor';
</span><span style="color: #008080;">326</span>
<span style="color: #008080;">327</span> <span style="color: #008000;">//If the program does not have the ternary operator, what can be used instead?
</span><span style="color: #008080;">328</span> <span style="color: #008000;">//
</span><span style="color: #008080;">329</span> <span style="color: #008000;">//can be replaced by if/else
</span><span style="color: #008080;">330</span> <span style="color: #008000;">//Sanyuanzhong is a simplified way of writing
</span><span style="color: #008080;">331</span> <span style="color: #008000;">//And the efficiency is not as high as if/esle
</span><span style="color: #008080;">332</span>
<span style="color: #008080;">333</span>
<span style="color: #008080;">334</span> <span style="color: #008000;">//======================================== ====
</span><span style="color: #008080;">335</span> <span style="color: #008000;">//Increment and decrement operators Return to original position
</span><span style="color: #008080;">336</span> <span style="color: #008000;">//
</span><span style="color: #008080;">337</span> <span style="color: #008000;">//Even if there is no increment or decrement in the language, it will not affect our writing of programs.</span><span style="color: #008080;">338</span> <span style="color: #008000;">//This is also a simplified way of writing some scenes
</span><span style="color: #008080;">339</span>
<span style="color: #008080;">340</span> <span style="color: #008000;">//Analysis, $b 1 is an arithmetic operation, and the calculated result is 3. This 3 is a ‘calculated result’ and has nothing to do with $b
</span><span style="color: #008080;">341</span> <span style="color: #008000;">//The result of this calculation is worth $a
</span><span style="color: #008080;">342</span> <span style="color: #008000;">//Therefore, $a is 3 and $b is 2</span>
<span style="color: #008080;">343</span> <span style="color: #800080;">$b</span> = 2<span style="color: #000000;">;
</span><span style="color: #008080;">344</span> <span style="color: #800080;">$a</span> = <span style="color: #800080;">$b</span> 1<span style="color: #000000;">;
</span><span style="color: #008080;">345</span> <span style="color: #0000ff;">echo</span> <span style="color: #800080;">$a</span>,'~',<span style="color: #800080;">$b</span>,'<br />'<span style="color: #000000;"> ;
</span><span style="color: #008080;">346</span>
<span style="color: #008080;">347</span> <span style="color: #008000;">//</span><span style="color: #008000;">$b, this is an incremental operation, and there must be a destination result when going.
</span><span style="color: #008080;">348</span> <span style="color: #008000;">//Question: What is the result of $b?
</span><span style="color: #008080;">349</span> <span style="color: #008000;">//Answer: $b, the result of the operation is $b itself
</span><span style="color: #008080;">350</span> <span style="color: #008000;">//Then change the value of $b to 1
</span><span style="color: #008080;">351</span> <span style="color: #008000;">//It is equivalent to return $b; $b = $b 1;
</span><span style="color: #008080;">352</span> <span style="color: #008000;">//$b =1;
</span><span style="color: #008080;">353</span> <span style="color: #008000;">//$a = $b;
</span><span style="color: #008080;">354</span> <span style="color: #008000;">//echo $a,'<br />',$b;
</span><span style="color: #008080;">355</span> <span style="color: #008000;">//
</span><span style="color: #008080;">356</span> <span style="color: #008000;">//
</span><span style="color: #008080;">357</span> <span style="color: #008000;">//==================================== =======</span>
<span style="color: #008080;">358</span> <span style="color: #008000;">/*</span><span style="color: #008000;">Bitwise operators, to put it bluntly, binary operators Return to original position
</span><span style="color: #008080;">359</span> <span style="color: #008000;">//People have 10 fingers, use decimal for easy calculation
</span><span style="color: #008080;">360</span> <span style="color: #008000;">//
</span><span style="color: #008080;">361</span> <span style="color: #008000;">//Mayans, don’t wear shoes, even toes are counted, round 20
</span><span style="color: #008080;">362</span> <span style="color: #008000;">//It doesn’t matter how much the carry is, the key is to facilitate our use
</span><span style="color: #008080;">363</span> <span style="color: #008000;">//
</span><span style="color: #008080;">364</span> <span style="color: #008000;">//For computers, all bits have only two states 0 1
</span><span style="color: #008080;">365</span> <span style="color: #008000;">//Because in the hundredth digit, 1 represents 100
</span><span style="color: #008080;">366</span> <span style="color: #008000;">//In carry of 10, 1 represents 10
</span><span style="color: #008080;">367</span> <span style="color: #008000;">//The ones digit, 1 represents 1
</span><span style="color: #008080;">368</span> <span style="color: #008000;">//
</span><span style="color: #008080;">369</span> <span style="color: #008000;">//We know that the information in the computer is stored as 0, 1
</span><span style="color: #008080;">370</span> <span style="color: #008000;">//One can store 0/1 units, called bits
</span><span style="color: #008080;">371</span> <span style="color: #008000;">//
</span><span style="color: #008080;">372</span> <span style="color: #008000;">//8 bits make up a byte, Byte
</span><span style="color: #008080;">373</span> <span style="color: #008000;">//Bytes are the most basic unit in computers.</span><span style="color: #008080;">374</span>
<span style="color: #008080;">375</span>
<span style="color: #008080;">376</span> <span style="color: #008000;">12 = 8 4;
</span><span style="color: #008080;">377</span> <span style="color: #008000;"> =1*2^3 1*2^2 0*2^1 0*2^0
</span><span style="color: #008080;">378</span> <span style="color: #008000;"> =1100
</span><span style="color: #008080;">379</span> <span style="color: #008000;">5=101
</span><span style="color: #008080;">380</span> <span style="color: #008000;">But in a computer, the most basic unit is a byte. There are 8 bits, but what if only 3 are used?
</span><span style="color: #008080;">381</span> <span style="color: #008000;">Answer: Write the 3 or 4 bits used on the right side of the byte
</span><span style="color: #008080;">382</span> <span style="color: #008000;"> These bits on the left are filled with 0s.
</span><span style="color: #008080;">383</span> <span style="color: #008000;">Therefore, in the computer:
</span><span style="color: #008080;">384</span> <span style="color: #008000;">12=0000 1100
</span><span style="color: #008080;">385</span> <span style="color: #008000;">5 =0000 0101
</span><span style="color: #008080;">386</span>
<span style="color: #008080;">387</span>
<span style="color: #008080;">388</span> <span style="color: #008000;">12 & 5 = 0000 0100 = 4
</span><span style="color: #008080;">389</span> <span style="color: #008000;">12 | 5 = 0000 1101 = 13
</span><span style="color: #008080;">390</span> <span style="color: #008000;">12 ^ 5 = 0000 1001 =9
</span><span style="color: #008080;">391</span> <span style="color: #008000;">Bitwise operator
</span><span style="color: #008080;">392</span> <span style="color: #008000;">& Bitwise AND , align the two binary values, treat 1 as true and 0 as false, and then perform AND operations on each bit.
</span><span style="color: #008080;">393</span> <span style="color: #008000;">|Bitwise OR, combine the two binary values, treat 1 as true, treat 0 as false, and then perform OR operation on each bit.
</span><span style="color: #008080;">394</span>
<span style="color: #008080;">395</span> <span style="color: #008000;">^Bitwise XOR: Align two binary values, treat 1 as true and 0 as false, and then perform XOR operation when each bit is different.</span><span style="color: #008080;">396</span>
<span style="color: #008080;">397</span>
<span style="color: #008080;">398</span> <span style="color: #008000;">Remind everyone: Computers are based on bit calculations. When we operate, we often use decimal directly.
</span><span style="color: #008080;">399</span> <span style="color: #008000;">*/</span>
<span style="color: #008080;">400</span> <span style="color: #008000;">//</span><span style="color: #008000;">================================ ==========</span>
<span style="color: #008080;">401</span>
<span style="color: #008080;">402</span> <span style="color: #800080;">$a</span> = 12<span style="color: #000000;">;
</span><span style="color: #008080;">403</span> <span style="color: #800080;">$a</span> = 0000 1100
<span style="color: #008080;">404</span> <span style="color: #008000;">//</span><span style="color: #008000;">Bitwise negation</span>
<span style="color: #008080;">405</span> <span style="color: #800080;">$a</span> = 1111 0011
<span style="color: #008080;">406</span> <span style="color: #0000ff;">echo</span> ~12
<span style="color: #008080;">407</span> <span style="color: #008000;">//</span><span style="color: #008000;">Representing negative numbers in computers is calculated using the two’s complement rule
</span><span style="color: #008080;">408</span> <span style="color: #008000;">//This is how to calculate negative numbers, assuming there are 8 digits
</span><span style="color: #008080;">409</span> <span style="color: #008000;">//The highest bit is 1, and the sign is negative
</span><span style="color: #008080;">410</span> <span style="color: #008000;">//
</span><span style="color: #008080;">411</span> <span style="color: #008000;">//Start the complement rule
</span><span style="color: #008080;">412</span> <span style="color: #008000;">//Calculate the absolute value of the other 7 bits except the sign bit
</span><span style="color: #008080;">413</span> <span style="color: #008000;">//(1)111 0011 =115
</span><span style="color: #008080;">414</span> <span style="color: #008000;">//Then absolute value -2^7 = 115 -128 = -13
</span><span style="color: #008080;">415</span> <span style="color: #008000;">//
</span><span style="color: #008080;">416</span> <span style="color: #008000;">//Therefore:
</span><span style="color: #008080;">417</span> <span style="color: #008000;">//1000 0001 ---Don’t take it for granted -1
</span><span style="color: #008080;">418</span> <span style="color: #008000;">//But 1-2^7 = -127</span>
<span style="color: #008080;">419</span> 1111 1111 --- 127-128 = -1
<span style="color: #008080;">420</span> 1000 0000 --- 0-128 =-128
<span style="color: #008080;">421</span>
<span style="color: #008080;">422</span> 0000 0000 --- 0
<span style="color: #008080;">423</span> 0111 1111 --- 127
<span style="color: #008080;">424</span>
<span style="color: #008080;">425</span> <span style="color: #008000;">//</span><span style="color: #008000;">Why someone asked: -128 127
</span><span style="color: #008080;">426</span> <span style="color: #008000;">//
</span><span style="color: #008080;">427</span> <span style="color: #008000;">//Intuitive understanding
</span><span style="color: #008080;">428</span> <span style="color: #008000;">//-128 --- 0 0 --- 127
</span><span style="color: #008080;">429</span> <span style="color: #008000;">//Bit operations are better mastered. Don’t worry if you are not familiar with them.
</span><span style="color: #008080;">430</span>
<span style="color: #008080;">431</span>
<span style="color: #008080;">432</span> <span style="color: #008000;">//======================================== ====
</span><span style="color: #008080;">433</span> <span style="color: #008000;">//Shift operation Return to original position</span>
<span style="color: #008080;">434</span>
<span style="color: #008080;">435</span> 5 = 0000 0101<span style="color: #000000;">;
</span><span style="color: #008080;">436</span> 5 << 1; <span style="color: #008000;">//</span><span style="color: #008000;">Move left
</span><span style="color: #008080;">437</span> <span style="color: #008000;">//Equivalent to multiplying by 2</span>
<span style="color: #008080;">438</span> 0000 1010; <span style="color: #008000;">//</span><span style="color: #008000;">The result is 10 </span>
<span style="color: #008080;">439</span> 5 >> 1; <span style="color: #008000;">//</span><span style="color: #008000;">Move right</span>
<span style="color: #008080;">440</span> 0000 0010
<span style="color: #008080;">441</span> <span style="color: #008000;">//</span><span style="color: #008000;">Equivalent to dividing by 2
</span><span style="color: #008080;">442</span>
<span style="color: #008080;">443</span>
<span style="color: #008080;">444</span> <span style="color: #008000;">//======================================== ====
</span><span style="color: #008080;">445</span> <span style="color: #008000;">//I learned about ‘quantity’ before – variables, constants
</span><span style="color: #008080;">446</span> <span style="color: #008000;">//Arithmetic operations can be performed between quantities, operators
</span><span style="color: #008080;">447</span> <span style="color: #008000;">//
</span><span style="color: #008080;">448</span> <span style="color: #008000;">//If there are only operations on quantities and quantities, then the knowledge we learn is only enough to make a calculator
</span><span style="color: #008080;">449</span>
<span style="color: #008080;">450</span> <span style="color: #008000;">//======================================== ====
</span><span style="color: #008080;">451</span> <span style="color: #008000;">//If you want to write a program: you must have a control structure
</span><span style="color: #008080;">452</span> <span style="color: #008000;">//
</span><span style="color: #008080;">453</span> <span style="color: #008000;">//The control structure is the conditions and logic that controls the execution order of the code
</span><span style="color: #008080;">454</span> <span style="color: #008000;">//
</span><span style="color: #008080;">455</span> <span style="color: #008000;">//Programmer uses php --- training --- computer
</span><span style="color: #008080;">456</span> <span style="color: #008000;">//if --- if
</span><span style="color: #008080;">457</span> <span style="color: #008000;">//else if ---else if
</span><span style="color: #008080;">458</span> <span style="color: #008000;">//otherwise ---- else </span>
<span style="color: #008080;">459</span> <span style="color: #800080;">$gender</span> = <span style="color: #800080;">$_GET</span>['gender'<span style="color: #000000;">];
</span><span style="color: #008080;">460</span> <span style="color: #0000ff;">if</span><span style="color: #000000;">(){
</span><span style="color: #008080;">461</span> }<span style="color: #0000ff;">else</span><span style="color: #000000;">{
</span><span style="color: #008080;">462</span>
<span style="color: #008080;">463</span> <span style="color: #000000;">}
</span><span style="color: #008080;">464</span> <span style="color: #008000;">//</span><span style="color: #008000;">============================== =============
</span><span style="color: #008080;">465</span>
<span style="color: #008080;">466</span> <span style="color: #008000;">//There are several control structures
</span><span style="color: #008080;">467</span> <span style="color: #008000;">//Answer: 1. Sequence, 2. Branch, 3. Loop
</span><span style="color: #008080;">468</span> <span style="color: #008000;">//These three control structures
</span><span style="color: #008080;">469</span> <span style="color: #008000;">//This is true for all languages Return to original position
</span><span style="color: #008080;">470</span>
<span style="color: #008080;">471</span> <span style="color: #008000;">//======================================== ====
</span><span style="color: #008080;">472</span> <span style="color: #008000;">// 1. Order
</span><span style="color: #008080;">473</span> <span style="color: #008000;">// The sequential structure means that the statements are executed in the order you wrote them, from front to back.
</span><span style="color: #008080;">474</span> <span style="color: #008000;">//Easiest to understand </span>
<span style="color: #008080;">475</span> <span style="color: #0000ff;">echo</span> 'a:8 o'clock','<br />'<span style="color: #000000;">;
</span><span style="color: #008080;">476</span> <span style="color: #0000ff;">echo</span> 'b:来YY:88354001','<br />'<span style="color: #000000;">;
</span><span style="color: #008080;">477</span> <span style="color: #0000ff;">echo</span> 'c:I understand','<br />'<span style="color: #000000;">;
</span><span style="color: #008080;">478</span> <span style="color: #0000ff;">echo</span> 'd: I started blogging','<br />'<span style="color: #000000;">;
</span><span style="color: #008080;">479</span>
<span style="color: #008080;">480</span> <span style="color: #008000;">//</span><span style="color: #008000;">================================== ==========
</span><span style="color: #008080;">481</span> <span style="color: #008000;">// 2. Branch <span style="color: #008000;">Return to original position</span>
</span><span style="color: #008080;">482</span> <span style="color: #008000;">//As the name suggests: there are branches, just like a road, after taking 3 forks, it’s time to choose one to go on.</span><span style="color: #008080;">483</span> <span style="color: #008000;">//The simplest, single-way branch
</span><span style="color: #008080;">484</span>
<span style="color: #008080;">485</span> <span style="color: #008000;">//Single branch </span>
<span style="color: #008080;">486</span> <span style="color: #800080;">$age</span> = 18<span style="color: #000000;">;
</span><span style="color: #008080;">487</span> <span style="color: #0000ff;">if</span>(<span style="color: #800080;">$age</span> >= 18<span style="color: #000000;"> ){
</span><span style="color: #008080;">488</span> <span style="color: #0000ff;">echo</span> 'You are an adult'<span style="color: #000000;">;
</span><span style="color: #008080;">489</span> }<span style="color: #008000;">//</span><span style="color: #008000;">The code in this if will either be executed or not
</span><span style="color: #008080;">490</span> <span style="color: #008000;">//The expression in brackets, if true, is executed, otherwise, is not executed </span>
<span style="color: #008080;">491</span> -----------------------------------------------
<span style="color: #008080;">492</span> <span style="color: #008000;">//</span><span style="color: #008000;">Double branch if /else </span>
<span style="color: #008080;">493</span> <span style="color: #800080;">$year</span> = 2012<span style="color: #000000;">;
</span><span style="color: #008080;">494</span> <span style="color: #800080;">$birth</span> = 1987<span style="color: #000000;">;
</span><span style="color: #008080;">495</span> <span style="color: #800080;">$age</span> = <span style="color: #800080;">$year</span> - <span style="color: #800080;">$birth</span>
<span style="color: #008080;">496</span> <span style="color: #0000ff;">if</span>(<span style="color: #800080;">$age</span> > 28<span style="color: #000000;">){
</span><span style="color: #008080;">497</span> <span style="color: #0000ff;">echo</span> 'You are middle-aged and old'<span style="color: #000000;">;
</span><span style="color: #008080;">498</span> }<span style="color: #0000ff;">else</span><span style="color: #000000;">{
</span><span style="color: #008080;">499</span> <span style="color: #0000ff;">echo</span> 'You are a promising young man'<span style="color: #000000;">;
</span><span style="color: #008080;">500</span> <span style="color: #000000;">}
</span><span style="color: #008080;">501</span> <span style="color: #008000;">//</span><span style="color: #008000;">if is true, then code segment 1 is executed
</span><span style="color: #008080;">502</span> <span style="color: #008000;">//if is false, then code segment 2 is executed
</span><span style="color: #008080;">503</span> <span style="color: #008000;">//Of the two codes in if else, one and only one will be executed.</span><span style="color: #008080;">504</span> <span style="color: #008000;">//---------------------------------- --------
</span><span style="color: #008080;">505</span> <span style="color: #008000;">//Multiple branches </span>
<span style="color: #008080;">506</span> <span style="color: #800080;">$age</span> = 34<span style="color: #000000;">;
</span><span style="color: #008080;">507</span> <span style="color: #0000ff;">if</span>( <span style="color: #800080;">$age</span> <=16<span style="color: #000000;"> ){
</span><span style="color: #008080;">508</span> <span style="color: #0000ff;">echo</span> 'Middle-aged'<span style="color: #000000;">;
</span><span style="color: #008080;">509</span> } <span style="color: #0000ff;">else</span> <span style="color: #0000ff;">if</span>(<span style="color: #800080;">$age</span> > 16 && <span style="color: #800080;">$age</span> <= 28 <span style="color: #000000;">){
</span><span style="color: #008080;">510</span> <span style="color: #0000ff;">echo</span> 'elderly'<span style="color: #000000;">;
</span><span style="color: #008080;">511</span> }<span style="color: #0000ff;">else</span> <span style="color: #0000ff;">if</span>( <span style="color: #800080;">$age</span> >28 && <span style="color: #800080;">$age</span> <=300 <span style="color: #000000;">){
</span><span style="color: #008080;">512</span> <span style="color: #0000ff;">echo</span> 'Other'<span style="color: #000000;">;
</span><span style="color: #008080;">513</span> <span style="color: #000000;">}
</span><span style="color: #008080;">514</span> ---------------------------------------- ---
<span style="color: #008080;">515</span> <span style="color: #008000;">//</span><span style="color: #008000;">switch branch statement <span style="color: #008000;">Return to original position</span></span>
<span style="color: #008080;">516</span>
<span style="color: #008080;">517</span> <span style="color: #800080;">$day</span> = 2<span style="color: #000000;">;
</span><span style="color: #008080;">518</span> <span style="color: #0000ff;">if</span>(<span style="color: #800080;">$day</span> == 1<span style="color: #000000;">){
</span><span style="color: #008080;">519</span> <span style="color: #0000ff;">echo</span> 'Monday'<span style="color: #000000;">;
</span><span style="color: #008080;">520</span> }<span style="color: #0000ff;">else</span> <span style="color: #0000ff;">if</span>(<span style="color: #800080;">$day</span> == 2<span style="color: #000000;">){
</span><span style="color: #008080;">521</span> <span style="color: #0000ff;">echo</span> 'Tuesday'<span style="color: #000000;">;
</span><span style="color: #008080;">522</span> }<span style="color: #0000ff;">else</span> <span style="color: #0000ff;">if</span>(<span style="color: #800080;">$day</span> == 3<span style="color: #000000;">){
</span><span style="color: #008080;">523</span> <span style="color: #0000ff;">echo</span> 'Wednesday'<span style="color: #000000;">;
</span><span style="color: #008080;">524</span> }<span style="color: #0000ff;">else</span> <span style="color: #0000ff;">if</span>(<span style="color: #800080;">$day</span> == 4<span style="color: #000000;">){
</span><span style="color: #008080;">525</span> <span style="color: #0000ff;">echo</span> 'Thursday'<span style="color: #000000;">;
</span><span style="color: #008080;">526</span> }<span style="color: #0000ff;">else</span> <span style="color: #0000ff;">if</span>(<span style="color: #800080;">$day</span> == 5<span style="color: #000000;">){
</span><span style="color: #008080;">527</span> <span style="color: #0000ff;">echo</span> 'Friday'<span style="color: #000000;">;
</span><span style="color: #008080;">528</span> }<span style="color: #0000ff;">else</span> <span style="color: #0000ff;">if</span>(<span style="color: #800080;">$day</span> == 6<span style="color: #000000;">){
</span><span style="color: #008080;">529</span> <span style="color: #0000ff;">echo</span> 'Saturday'<span style="color: #000000;">;
</span><span style="color: #008080;">530</span> }<span style="color: #0000ff;">else</span> <span style="color: #0000ff;">if</span>(<span style="color: #800080;">$day</span> == 7<span style="color: #000000;">){
</span><span style="color: #008080;">531</span> <span style="color: #0000ff;">echo</span> 'Sunday'<span style="color: #000000;">;
</span><span style="color: #008080;">532</span> }<span style="color: #0000ff;">else</span><span style="color: #000000;">{
</span><span style="color: #008080;">533</span> <span style="color: #0000ff;">echo</span> 'Does not exist'<span style="color: #000000;">;
</span><span style="color: #008080;">534</span> <span style="color: #000000;">}
</span><span style="color: #008080;">535</span> <span style="color: #008000;">//</span><span style="color: #008000;">For the value of a variable, there are many possibilities. It is of course possible to use if / if else to compare.</span><span style="color: #008080;">536</span> <span style="color: #008000;">//However, there is a simpler branch structure to replace it</span>
<span style="color: #008080;">537</span>
<span style="color: #008080;">538</span>
<span style="color: #008080;">539</span> <span style="color: #800080;">$day</span> =2<span style="color: #000000;">;
</span><span style="color: #008080;">540</span> <span style="color: #0000ff;">switch</span>(<span style="color: #800080;">$day</span><span style="color: #000000;">){
</span><span style="color: #008080;">541</span> <span style="color: #0000ff;">case</span> 1:
<span style="color: #008080;">542</span> <span style="color: #0000ff;">echo</span> 'Monday'<span style="color: #000000;">;
</span><span style="color: #008080;">543</span> <span style="color: #0000ff;">break</span><span style="color: #000000;">;
</span><span style="color: #008080;">544</span> <span style="color: #0000ff;">case</span> 2:
<span style="color: #008080;">545</span> <span style="color: #0000ff;">echo</span> 'Tuesday'<span style="color: #000000;">;
</span><span style="color: #008080;">546</span> <span style="color: #0000ff;">break</span><span style="color: #000000;">;
</span><span style="color: #008080;">547</span> <span style="color: #0000ff;">case</span> 3:
<span style="color: #008080;">548</span> <span style="color: #0000ff;">echo</span> 'Wednesday'<span style="co"></span>
Copy after login