PHP 7.1.0 Release Candidate 3 Released

preg_quote

(PHP 4, PHP 5, PHP 7)

preg_quoteQuote 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: . \ + * ? [ ^ ] $ ( ) { } = ! < > | : -

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
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

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User Contributed Notes 2 notes

up
34
Anonymous
8 years ago
Wondering why your preg_replace fails, even if you have used preg_quote?

Try adding the delimiter / - preg_quote($string, '/');
up
7
zooly
7 years ago
To escape characters with special meaning, like: .-[]() and so on, use \Q and \E.

For example:

<?php echo ( preg_match('/^'.( $myvar = 'te.t' ).'$/i', 'test') ? 'match' : 'nomatch' ); ?>

Will result in: match

But:

<?php echo ( preg_match('/^\Q'.( $myvar = 'te.t' ).'\E$/i', 'test') ? 'match' : 'nomatch' ); ?>

Will result in: nomatch
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