preg_quote

Quote regular expression characters

Description

string preg_quote(string $str, stringnull $delimiter = null)

preg_quote takes str and 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: . \ + * ? [ ^ ] $ ( ) { } = ! < > | : - #

Note that / is not a special regular expression character.

Note:

Note that preg_quote is not meant to be applied to the $replacement string(s) of preg_replace etc.

Parameters

str

The input string.

delimiter

If the optional delimiter is specified, 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.

Return Values

Returns the quoted (escaped) string.

Changelog

Version Description
7.3.0 The # character is now quoted
7.2.0 delimiter is nullable now.

Examples

Example #1 preg_quote example

<?php
$keywords = '$40 for a g3/400';
$keywords = preg_quote($keywords, '/');
echo $keywords; // returns \$40 for a g3\/400
?>

Example #2 Italicizing a word within some text

<?php
// In this example, preg_quote($word) is used to keep the
// asterisks from having special meaning to the regular
// expression.

$textbody = "This book is *very* difficult to find.";
$word = "*very*";
$textbody = preg_replace ("/" . preg_quote($word, '/') . "/",
                          "<i>" . $word . "</i>",
                          $textbody);
?>

Notes

Note: This function is binary-safe.

See Also