PHP Operator (5) 'Logical Operator' Example Explanation

$m || $n or $m or $n

PS: It should be noted here that the two operators logical AND and logical OR have four operation symbols ("&&", "and", "||", "or"), although they They belong to the same logical structure, such as logical or (|| and or), but they have different priorities. We will use an example to illustrate this later.

Regarding priority, make a simple comparison here. The result of 1+2*5 is 11 instead of 15. This is because of the priority ratio of multiplication "*" The addition "+" has high priority. So PHP operators also have priority.

Logical Operator Example

In this example we use the operation symbols "||" and "or" in logical OR to perform the same judgment operation, but because "||" and "or" have different priorities, so the results they return are also different. The code is as follows

<?php
header("Content-type:text/html;charset=utf-8");  //什么使用UTF-8编码
$a = true;             //声明一个布尔型变量$a，赋值为真
$b = true;             //声明一个布尔型变量$b，赋值为真
$c = false;            //声明一个初值为假的布尔型变量$c

if($a or $b and $c){      //用or做判断
    echo "真";
}else{
    echo "假";
}

echo "<br/>";

if($a || $b and $c){      //用||做判断
    echo "真";
}else{
    echo "假";
}

?>

Code running results:

In the above example, we used the same if statement, but used different operators "or" and "||", but the returned results are completely opposite, so in practical applications, it must Pay more attention to the details of operator priority.

So far I have introduced you to "arithmetic operators", "string operators", "assignment operators", "bit operators", plus Today, we have learned five types of "logical operators". In the next section, we will explain to you the sixth type of PHP operator "Comparison operator" .

Recommended related articles:

1.PHP Operator (1) "Arithmetic Operator" Example Example

2.PHP Operator (2) Detailed Example of "String Operator"

3. PHP Operator (3) "Assignment Operator" Example Example

4.PHP Operator (4) "Bit Operator" Example Example