Detailed explanation of commonly used regular expression functions in PHP

This article mainly shares with you the detailed explanation of commonly used regular expression functions in PHP, hoping to help everyone.

Statement: $pattern=regular expression, $subject=target data

1.preg_match() and preg_match_all()

preg_match($pattern,$subject,[array &$matches])
preg_match_all($pattern,$subject,array &$matches)

preg_match will only match once, preg_match_all will All matching strings are matched and placed in the matches array, and both functions have an integer return value.

return The number of times the result is matched;

We can also know the number of key-value pairs in matches through the function return value.

Let’s give a chestnut to experience:

<?php  
//preg_match ,preg_match_all  
$pattern = &#39;/[0-9]/&#39;;  
$subject = &#39;weuyr3ui76as83s0ck9&#39;;  
$m1 = $m2 = array();  
preg_match($pattern,$subject,$m1);  
preg_match_all($pattern,$subject,$m2);  
show($m1);  
echo &#39;<hr>&#39;;  
show($m2);  
function show($var = null){  
    if(empty($var)){  
        echo &#39;null&#39;;  
    }  
    else if(is_array($var)||is_object($var)){  
        //array,object  
        echo &#39;<pre class="brush:php;toolbar:false">&#39;;  
        print_r($var);  
        echo &#39;

'; } else{ //string ,int ,float... echo $var; } } ?>

The above code is to find the number in the string weuyr3ui76as83s0ck9.

2.preg_replace() and preg_filter()

preg_replace($pattern,$replacemenrt,$subject)
preg_filter($pattern,$replacement,$subject)

Let’s give an example:

<?php  
//preg_filter() preg_replace()  
$pattern = &#39;/[0-9]/&#39;;  
$subject =&#39;weuyr3ui76as83s0ck9&#39;;  
$replacement = &#39;球宝宝&#39;;  
$str1 = preg_replace($pattern,$replacement,$subject);  
$str2 = preg_filter($pattern,$replacement,$subject);  
show($str1);  
echo &#39;<hr>&#39;;  
show($str2);  
function show($var = null){  
    if(empty($var)){  
        echo &#39;null&#39;;  
    }  
    else if(is_array($var)||is_object($var)){  
        //array,object  
        echo &#39;<pre class="brush:php;toolbar:false">&#39;;  
        print_r($var);  
        echo &#39;

'; } else{ //string ,int ,float... echo $var; } } ?>

In preg_replacement(), not only strings can be used, but also Use an array.

Just need: $pattern = array('/[0-3]/','[4-6]','[7-9]');

$replacement = array('ball','bao','bao');

This means that when a number between 0-3 is matched, "ball" will be used instead; when it matches 4-6 When matching a certain number in , use "宝" to replace it; when matching a certain number in 7-9, use "宝" to replace it.

For example:

<?php  
//preg_filter() preg_replace()  
//$pattern = &#39;/[0-9]/&#39;  
$pattern = array(&#39;/[0-3]/&#39;,&#39;/[4-6]/&#39;,&#39;/[7-9]/&#39;);  
$subject =&#39;weuyr3ui76as83s0ck9&#39;;  
//$replacement = &#39;球宝宝&#39;;  
$replacement = array(&#39;球&#39;,&#39;宝&#39;,&#39;宝&#39;);  
$str1 = preg_replace($pattern,$replacement,$subject);  
$str2 = preg_filter($pattern,$replacement,$subject);  
show($str1);  
echo &#39;<hr>&#39;;  
show($str2);  
function show($var = null){  
    if(empty($var)){  
        echo &#39;null&#39;;  
    }  
    else if(is_array($var)||is_object($var)){  
        //array,object  
        echo &#39;<pre class="brush:php;toolbar:false">&#39;;  
        print_r($var);  
        echo &#39;

'; } else{ //string ,int ,float... echo $var; } } ?>

Since the results of preg_filter() and preg_replacement() are the same in the above two examples, what is the difference between them?

When we add $subject = array('weuy','r3ui','76as83','s','0ck9');, the difference between them will be shown:

a974b541f0baaa3fbdc2e2536727118c';  
show($str2);  
  
function show($var = null){  
    if(empty($var)){  
        echo 'null';  
    }  
    else if(is_array($var)||is_object($var)){  
        //array,object  
        echo 'e03b848252eb9375d56be284e690e873';  
        print_r($var);  
        echo 'bc5574f69a0cba105bc93bd3dc13c4ec';  
    }  
    else{  
        //string ,int ,float...  
        echo $var;  
    }  
}  
?>

It can be seen from the above:

The preg_replacement() function will be displayed regardless of whether there is a replaced word, but the preg_filter() function will not be displayed if there is no replaced word.

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