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Summary of how to use operators in php_PHP tutorial

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Jul 13, 2016 pm 05:15 PM

a++ php 。 code Instructions copy Summarize arithmetic operator Decreasing Increment

Arithmetic operators

1. Arithmetic operators: +, -, *, /, %.

2. Increment/decrement operators: such as $a++,$a--,++$a,--$a.

For example:

The code is as follows Copy code

代码如下

复制代码

$a=10;
$b=5;
$c=$a++; //先赋值，后自增。$c=$a,$a=$a+1
$d=$b--; //先赋值，后自减。$d=$b,$b=$a-1
echo '$a='.$a."||".'$c='.$c.'
'; //$a=11,$c=10
echo '$b='.$b."||".'$d='.$d.'
'; //$b=4,$d=5
?>

$a=10;
$b=5;
$c=++$a; //先自增，后赋值。$a=$a+1，$c=$a
$d=--$b; //先自减，后赋值。$b=$a-1, $d=$b
echo '$a='.$a."||".'$c='.$c.'
'; //$a=11,$c=11
echo '$b='.$b."||".'$d='.$d.'
'; //$b=4,$d=4
?>

$a=10; $b=5; $c=$a++; //Assign value first, then increment. $c=$a,$a=$a+1

$d=$b--; //Assign value first, then decrement. $d=$b,$b=$a-1

echo '$a='.$a."||".'$c='.$c.'
'; //$a=11,$c=10
echo '$b='.$b."||".'$d='.$d.'
'; //$b=4,$d=5

$a=10;

代码如下	复制代码
$a>$b ? print "Yes" : ""; $a>$b ? '': print 'No';

$b=5;

$c=++$a; //increment first, then assign value. $a=$a+1，$c=$a

$d=--$b; //decrement first, then assign value. $b=$a-1, $d=$b

echo '$a='.$a."||".'$c='.$c.'
'; //$a=11,$c=11

echo '$b='.$b."||".'$d='.$d.'
'; //$b=4,$d=4

代码如下	复制代码
$str = $_GET['abc'] ? 'wangjinbo' : 'wjb';

Ternary operator

(expr1) ? (expr2) : (expr3); Explanation: If condition "expr1" is true, execute statement "expr2", otherwise execute "expr3".

The following statements are syntactically correct, they omit the second or third "element" in small dequotation marks:

代码如下

复制代码

$a=10;$b=7;
if($a++>8 || $b++>7){ //$a++>8为真，$b++>7这个就不执行了
echo 'OK!';
}
echo 'a='.$a.'b='.$b; // 输出OK，a=11,b=7

改变一下

$a=10;$b=7;
if($a++>10 && $b++>7){ //$a++>8为假，$b++>7这个就不执行了
echo 'OK!';
}
echo 'a='.$a.'b='.$b; // a=11,b=7

The code is as follows	Copy code
$a>$b ? print "Yes" : ""; $a>$b ? '': print 'No';

It should be noted that when using the ternary operator, it is recommended to use the print statement instead of the echo statement. Pay attention to the understanding of the following series of sentences:

The code is as follows	Copy code
$str = $_GET['abc'] ? 'wangjinbo' : 'wjb';

This cannot be understood as: when $str is equal to $_GET['abc'], the assignment is 'wangjinbo' otherwise the assignment is 'wjb'; reason one: == should be used to judge equality; reason two: ternary operator The syntax is as shown above: (expr1) ? (expr2) : (expr3), obviously the above binary, ternary 'wangjinbo' or 'wjb' cannot form a meaningful expression alone; The correct understanding is: when $_GET['abc'] is empty (that is, whether '', null, 0, undifine in PHP are all equivalent to the Boolean value false), assign $str to 'wangjinbo' , otherwise the value is 'wjb'; Logical operators: For example:

The code is as follows	Copy code
$a=10;$b=7; if($a++>8 \|\| $b++>7){ //$a++>8 is true, $b++>7 will not be executed echo 'OK!'; } echo 'a='.$a.'b='.$b; // Output OK, a=11,b=7 Change it up $a=10;$b=7; if($a++>10 && $b++>7){ //$a++>8 is false, $b++>7 will not be executed echo 'OK!'; } echo 'a='.$a.'b='.$b; // a=11,b=7

Details: and && both represent logical AND, what is their difference?

Mainly reflected in priority

Priority of and

代码如下	复制代码
and< = <&& or < = < \|\| 如： $a=false \|\| true; //&& > = > and ;先比较false \|\| true，再赋值 $b=false or true; //\|\| > = > or ；先赋值$b=false，再比较，所以结果是false var_dump($a,$b); //bool(true) bool(false)

Bitwise operators

Displacement is a mathematical operation in PHP. Bits moved out in any direction are discarded. When shifting left, the right side is padded with zeros, and the sign bit is moved away, meaning that the sign is not preserved. When shifting right, the left side is padded with sign bits, which means the sign is preserved.

Use parentheses to ensure desired precedence. For example, $a & $b == true performs comparison first and then performs bitwise AND; while ($a & $b) == true performs bitwise AND first and then performs comparison.

Pay attention to data type conversion. If both left and right arguments are strings, the bitwise operators operate on the ASCII values of the characters.

PHP’s ini setting error_reporting uses bitwise values,
Real-life examples of turning off a bit are provided. To show except prompt level
For all errors except php.ini, use this:
E_ALL & ~E_NOTICE

The specific operation method is to first obtain the value of E_ALL:
00000000000000000111011111111111
Then get the value of E_NOTICE:
00000000000000000000000000001000
Then negate it via ~:
11111111111111111111111111110111
Finally, use bitwise AND (&) to get the bits that are set (to 1) in both values:
00000000000000000111011111110111

Another method is to use bitwise XOR (^) to get only the values in
The bits set in one of the values:
E_ALL ^ E_NOTICE

error_reporting can also be used to demonstrate how to set the bit. Show only errors and recoverables
The wrong way is:
E_ERROR | E_RECOVERABLE_ERROR

That is to say, E_ERROR
00000000000000000000000000000001
and E_RECOVERABLE_ERROR
00000000000000000001000000000000
Use the bitwise OR (|) operator to get the result of a bit being set in any value:
00000000000000000001000000000001

Example #1 AND, OR and XOR bitwise operators for integers

The code is as follows

Copy code

代码如下

复制代码

/*
* Ignore the top section,
* it is just formatting to make output clearer.
*/

$format = '(%1d = %1b) = (%2d = %2b)'
. ' %3$s (%4d = %4b)' . "n";

echo << --------- --------- -- ---------
result value op test
--------- --------- -- ---------
EOH;

/*
* Here are the examples.
*/

$values = array(0, 1, 2, 4, 8);
$test = 1 + 4;

echo "n Bitwise AND n";
foreach ($values as $value) {
$result = $value & $test;
printf($format, $result, $value, '&', $test);
}

echo "n Bitwise Inclusive OR n";
foreach ($values as $value) {
$result = $value | $test;
printf($format, $result, $value, '|', $test);
}

echo "n Bitwise Exclusive OR (XOR) n";
foreach ($values as $value) {
$result = $value ^ $test;
printf($format, $result, $value, '^', $test);
}
?>
以上例程会输出：

---------     --------- -- ---------
result        value      op test
---------     --------- -- ---------
Bitwise AND
( 0 = 0000) = ( 0 = 0000) & ( 5 = 0101)
( 1 = 0001) = ( 1 = 0001) & ( 5 = 0101)
( 0 = 0000) = ( 2 = 0010) & ( 5 = 0101)
( 4 = 0100) = ( 4 = 0100) & ( 5 = 0101)
( 0 = 0000) = ( 8 = 1000) & ( 5 = 0101)

Bitwise Inclusive OR
( 5 = 0101) = ( 0 = 0000) | ( 5 = 0101)
( 5 = 0101) = ( 1 = 0001) | ( 5 = 0101)
( 7 = 0111) = ( 2 = 0010) | ( 5 = 0101)
( 5 = 0101) = ( 4 = 0100) | ( 5 = 0101)
(13 = 1101) = ( 8 = 1000) | ( 5 = 0101)

Bitwise Exclusive OR (XOR)
( 5 = 0101) = ( 0 = 0000) ^ ( 5 = 0101)
( 4 = 0100) = ( 1 = 0001) ^ ( 5 = 0101)
( 7 = 0111) = ( 2 = 0010) ^ ( 5 = 0101)
( 1 = 0001) = ( 4 = 0100) ^ ( 5 = 0101)
(13 = 1101) = ( 8 = 1000) ^ ( 5 = 0101)

/*<🎜> * Ignore the top section,<🎜> * it is just formatting to make output clearer.<🎜> */<🎜> <🎜>$format = '(%1$2d = %1$04b) = (%2$2d = %2$04b)'<🎜> . ' %3$s (%4$2d = %4$04b)' . "n";<🎜> <🎜>echo << --------- --------- -- ---------<🎜> result value op test<🎜> --------- --------- -- ---------<🎜> EOH;<🎜> <🎜><🎜> /*<🎜> * Here are the examples.<🎜> */<🎜> <🎜>$values = array(0, 1, 2, 4, 8);<🎜> $test = 1 + 4;<🎜> <🎜>echo "n Bitwise AND n";<🎜> foreach ($values as $value) {<🎜> $result = $value & $test;<🎜> Printf($format, $result, $value, '&', $test);<🎜> }<🎜> <🎜>echo "n Bitwise Inclusive OR n";<🎜> foreach ($values as $value) {<🎜> $result = $value | $test;<🎜> Printf($format, $result, $value, '|', $test);<🎜> }<🎜> <🎜>echo "n Bitwise Exclusive OR (XOR) n";<🎜> foreach ($values as $value) {<🎜> $result = $value ^ $test;<🎜> Printf($format, $result, $value, '^', $test);<🎜> }<🎜> ?> The above routine will output: --------- --------- -- --------- result value op test --------- --------- -- --------- Bitwise AND ( 0 = 0000) = ( 0 = 0000) & ( 5 = 0101) ( 1 = 0001) = ( 1 = 0001) & ( 5 = 0101) ( 0 = 0000) = ( 2 = 0010) & ( 5 = 0101) ( 4 = 0100) = ( 4 = 0100) & ( 5 = 0101) ( 0 = 0000) = ( 8 = 1000) & ( 5 = 0101) Bitwise Inclusive OR ( 5 = 0101) = ( 0 = 0000) | ( 5 = 0101) ( 5 = 0101) = ( 1 = 0001) | ( 5 = 0101) ( 7 = 0111) = ( 2 = 0010) | ( 5 = 0101) ( 5 = 0101) = ( 4 = 0100) | ( 5 = 0101) (13 = 1101) = ( 8 = 1000) | ( 5 = 0101) Bitwise Exclusive OR (XOR) ( 5 = 0101) = ( 0 = 0000) ^ ( 5 = 0101) ( 4 = 0100) = ( 1 = 0001) ^ ( 5 = 0101) ( 7 = 0111) = ( 2 = 0010) ^ ( 5 = 0101) (1 = 0001) = (4 = 0100) ^ (5 = 0101) (13 = 1101) = ( 8 = 1000) ^ ( 5 = 0101)

Comparison operators

If comparing a number to a string or comparing strings involving numeric content, the string is converted to a numeric value and the comparison is performed as a numeric value. This rule also applies to switch statements. When comparing with === or !==, no type conversion is performed because both types and values are compared.

The code is as follows Copy code

代码如下

复制代码

var_dump(0 == "a"); // 0 == 0 -> true
var_dump("1" == "01"); // 1 == 1 -> true
var_dump("10" == "1e1"); // 10 == 10 -> true
var_dump(100 == "1e2"); // 100 == 100 -> true

switch ("a") {
case 0:
    echo "0";
    break;
case "a": // never reached because "a" is already matched with 0
    echo "a";
    break;
}
?>

var_dump(0 == "a"); // 0 == 0 -> true
var_dump("1" == "01"); // 1 == 1 -> true
var_dump("10" == "1e1"); // 10 == 10 -> true
var_dump(100 == "1e2"); // 100 == 100 -> true

switch ("a") {
case 0:
echo "0";
Break;
case "a": // never reached because "a" is already matched with 0
echo "a";
Break;
}
?>

**比较多种类型**
运算数 1 类型	运算数 2 类型	结果
null 或 string	string	将 `<font face="NSimsun">NULL</font>` 转换为 ""，进行数字或词汇比较
bool 或 null	任何其它类型	转换为 bool，`<font face="NSimsun">FALSE</font>` < `<font face="NSimsun">TRUE</font>`
object	object	内置类可以定义自己的比较，不同类不能%

For multiple types, comparison operators compare according to the following table (in order).

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