Quote regular expression characters

preg_match
preg_replace_callback_array
PCRE Functions
PHP Manual

# preg_quote

(PHP 4, PHP 5, PHP 7)

preg_quote — Quote regular expression characters

### Description

string preg_quote ( string `$str` [, string `$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: . \ + * ? [ ^ ] $ ( ) { } = ! < > | : -

### 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
--- | ---
5.3.0 | The - character is now quoted

### 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

- PCRE Patterns
- escapeshellcmd() - Escape shell metacharacters

preg_match
preg_replace_callback_array
PCRE Functions
PHP Manual