Introduction to the use of logical operators in php

Introduction to the use of logical operators in php_PHP tutorial

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Release： 2016-07-13 17:16:21

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Logical operators in php include not equal to, or, and, and not (the priority is: ! > && > || > and > xor > or). Let me introduce to you the logical operations in php. How to use the symbol.

Note:

The priority is: ! > && > || > and > xor > or
Also note that although ! has higher precedence than =, PHP still allows expressions like the following: if (!$a = foo()), in this case the output of foo() is assigned to $a .

First look at the manual and I agree with a sentence in the manual: using brackets can enhance the readability of the code.

例子	名称	结果
$a and $b	And（逻辑与）	`TRUE`，如果 $a 与 $b 都为 `TRUE`。
$a or $b	Or（逻辑或）	`TRUE`，如果 $a 或 $b 任一为 `TRUE`。
$a xor $b	Xor（逻辑异或）	`TRUE`，如果 $a 或 $b 任一为 `TRUE`，但不同时是。
! $a	Not（逻辑非）	`TRUE`，如果 $a 不为 `TRUE`。
$a && $b	And（逻辑与）	`TRUE`，如果 $a 与 $b 都为 `TRUE`。
$a \|\| $b	Or（逻辑或）	`TRUE`，如果 $a 或 $b 任一为 `TRUE`。

Example

In php, "|" is a php bit operator, and "||" is a logical operator

Bitwise operator code:

The code is as follows

代码如下	复制代码
$a=0; $b=0; if($a=3 \| $b=3){ $a++; $b++; } echo $a.','.$b; //输出 4,4 ?>

Copy code

代码如下

复制代码

$a=0;
$b=0;
if($a=3 || $b=3){
$a++;
$b++;
}
echo $a.','.$b; //输出 1,1
?>

$a=0;

$b=0;

if($a=3 | $b=3){

$a++;
$b++;

} echo $a.','.$b; //Output 4,4 ?> Compare the code, the following is the code of the logical operator:

The code is as follows

Copy code

$a=0;<🎜> $b=0;<🎜> if($a=3 || $b=3){<🎜> $a++;<🎜> $b++;<🎜> }<🎜> echo $a.','.$b; //Output 1,1<🎜> ?> In the above two examples, in the first example, "$a=3 | $b=3", since the priority of "|" is higher than the assignment operator, the order of operations can be written as "$a =(3 | $b=3)", first $b is assigned the value 3, and $a is assigned the value of the binary number 0100 | 0100, which is still 0100, so $a is assigned the value 0100 at this time, which is decimal 3. The assignment is successful, true is returned, and the content in the if code block is executed. $a is incremented, and $b is also incremented. Therefore, $a=4, $b=4 In the second example, it can also be seen as "$a = (3 || $b = 3)". First, 3||$b=3 returns true, "||" causes a short circuit, and the "||" before 3 is already true, "$b=3" is no longer executed, so $b is still 0 at this time, $a is true of Boolean type, the assignment is successful, true is returned, the content in the if code block is executed, and $a++ returns is true, $b++ is 1, so, $a=1,$b=1