Detailed explanation of commonly used regular expression functions in PHP-PHP Tutorial-php.cn

Detailed explanation of commonly used regular expression functions in PHP

小云云

Release： 2023-03-22 09:44:01

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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)

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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; } } ?>

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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)

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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; } } ?>

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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; } } ?>

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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:

<?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;;  
$subject = array(&#39;weuy&#39;,&#39;r3ui&#39;,&#39;76as83&#39;,&#39;s&#39;,&#39;0ck9&#39;);  
//$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; } } ?>

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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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