Detailed introduction to php operators and expressions_php examples

php operators and expressions

1. Classification of operators

1. Classification by operands

1.!true // Unary operator
2.$a+$b // Binary operator
3.true ? 1:0 // Ternary operator

2. Classification by operation function

(1) Arithmetic operators
1.+,-,x,/,%(remainder)

(2) String operators
1.. // For example: $a = 'abc'.'efg';

(3) Assignment operator

1.= // Simple assignment
2.+=, -=, X=, /=, %=, .= // Compound assignment
3.++($a++,++$a), --($a--,--$a) // Increasingly decreasing
4.&($a = 1;$b = &a) // Reference assignment

(4) Comparison Operator

1.==, ===(constantly equal to), !=, !===, <>(not equal to), <, >, <=, >=

(5) Logical operators
1.// The priority inside the brackets is higher than the priority outside the brackets
2.&&(and), ||(or), !(not), xor(exclusive or),

(6) bit operators
1.&(bitwise AND), |(bitwise OR), ~(bitwise NOT), ^(bitwise XOR), <<(left shift), >>(right shift)

2. Arithmetic operators

% remainder, common usage: 1) Integer division operation 2) Control the value range

Example: Determine whether it is a leap year (one leap year every four years, no leap year in one hundred years, and another leap year in four hundred years)

// %会把两边的数转成整型后在整除
// %两边不能用小数或负数
if ((($year%4 == 0) && ($year%100 != 0)) || $year%400 == 0)
echo "闰年";
else
echo "平年";

3. Assignment operator

//先自身加10，然后赋值给自己，等价于 $a=$a+10
$a += 10;
 
//前置递增递减，先递增递减再赋值
++$a

//先赋值，再递增递减
$a++ 
//实例
$a = 10;
$b = $a++
$c = --$b
结果：a=11 b=9 c=9

4. Logical operators

xor XOR: The same is false (two true or two false = false), different is true (one true and one false = false)
Tips: Pay attention to the difference with or, the two truths of or = true
Logical operator short circuit
1. && //If one is false, no operation will be performed on the following, it must be false
2. || //If one is true, no operation will be performed later, and it must be true

fopen ("test.php","r") or die("failure");

Tips: There is no short-circuit feature for operator & |

5. Bitwise operators

Bit operation: Convert integer to 32-bit binary, and convert string to ANSCA code for processing

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