How to remove non-alphanumeric characters from string in PHP? (code example)

In PHP, you can use the preg_replace() function to use regular expressions to delete non-alphanumeric characters in a string. The following article will introduce to you how the preg_replace() function deletes non-alphanumeric characters in a string. I hope it will be helpful to you.

preg_replace() function

First let’s take a look at the preg_replace() function.

The preg_replace() function can execute a regular expression to search or replace strings of all symbol conditions through the rules defined by this regular expression.

Basic syntax:

preg_match( $pattern, $replacement_string, $original_string )

Parameters:

$pattern parameters: Regular expression, indicating the rules for searching and replacing in strings.

$replacement_string parameter: Indicates the string used for replacement.

$original_string parameter: Indicates the original string that needs to be searched or replaced.

Return value:

1. When a match is found and replaced, the modified string will be returned.

2. If no match is found, the original string remains unchanged and returned as is.

Delete non-alphanumeric characters in the string

Let’s take a simple look at how the preg_replace() function deletes of non-alphanumeric characters in a string.

Example 1: Use the regular expression '/[\W]/'Match all non-alphanumeric characters and replace them with '' (empty string).

<?php  
$str="$#*@php中文网，2018-12-29！";
echo("原字符串：<br>");  
echo($str); 
echo("<br><br>"); 
$str = preg_replace( &#39;/[\W]/&#39;, &#39;&#39;, $str); 
echo("修改后的字符串：<br>");  
echo($str); 
?>

Note: In regular expressions, W is a metacharacter preceded by a backslash (\W), which is used to give the combination special meaning. It represents a combination of non-alphanumeric characters.

Output:

Example 2: Match using regular expression '/[^ a-z0-9]/i' All non-alphanumeric characters and replace them with '' (empty string).

<?php  
$str="$#*@www.php.cn！2018-12-29？";
echo("原字符串：<br>");  
echo($str); 
echo("<br><br>"); 
$str = preg_replace( &#39;/[^a-z0-9]/i&#39;, &#39;&#39;, $str); 
echo("修改后的字符串：<br>");  
echo($str); 
?>

Output:

Description: In the regular expression '/[^ a-z0-9]/i'

1. i: used for case insensitivity.

2. az: It is used for all lowercase letters. Because i has been mentioned in the statement (not case-sensitive), there is no need to specify AZ.

3, 0-9: used to match all numbers.

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