PHP Function Reference

PHP preg_quote() Function



The PHP preg_quote() function puts a backslash in front of every character that is part of the regular expression syntax. This is useful if you have a run-time string that you need to match in some text and the string may contain special regex characters.

The special regular expression characters are: . \ + * ? [ ^ ] $ ( ) { } = ! < > | : - #

Please note that / is not a special regular expression character.

Syntax

preg_quote(str, delimiter)

Parameters

str Required. Specify the input string.
delimiter Optional. When specified (a single character), it will also be escaped. This is useful for escaping the delimiter that is required by the PCRE functions. The / is the most commonly used delimiter. Default is null.

Return Value

Returns the quoted (escaped) string.

Example: preg_quote() example

The example below shows the usage of preg_quote() function.

<?php
//a string which need to be escaped
$str = 'send $100 to D/303';

//using preg_quote function 
$str = preg_quote($str, '/');

//displaying the result
echo $str;
?>

The output of the above code will be:

send \$100 to D\/303

Example: italicizing a word within given text

In the example below a word containing asterisks is italicized. As asterisk has special meaning in the regular expression. Therefore it is first escaped using preg_quote() function.

<?php
//asterisk has special meaning in the regular 
//expression, therefore it should be escaped first
$str = "This book is *very* difficult to find.";

$word = "*very*";

//italicizing the $word
$str = preg_replace ("/".preg_quote($word, '/')."/",
                     "<i>".$word."</i>", $str);

//displaying the result
echo $str;
?>

The output of the above code will be:

This book is <i>*very*</i> difficult to find.

❮ PHP RegEx Reference