Last updated: Fri, 03 Sep 2010

preg_quote

(PHP 4, PHP 5)

preg_quote — 正規表現文字をクオートする

説明

string preg_quote ( string $str [, string $delimiter = NULL ] )

preg_quote() は、str を引数とし、正規表現構文の特殊文字の前にバックスラッシュを挿入します。この関数は、実行時に生成される文字列をパターンとしてマッチングを行う必要があり、その文字列には正規表現の特殊文字が含まれているかも知れない場合に有用です。

正規表現の特殊文字は、次のものです。 . \ + * ? [ ^ ] $ ( ) { } = ! < > | : -

パラメータ

str: 入力文字列。
delimiter: オプションの delimiter を指定すると、ここで指定した文字もエスケープされます。これは、PCRE 関数が使用するデリミタをエスケープする場合に便利です。'/' がデリミタとしては最も一般的に使用されています。

返り値

クォートされた文字列を返します。

変更履歴

バージョン	説明
5.3.0	- 文字がクォートされるようになりました。

例

例1 preg_quote() の例


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

例2 テキスト内の単語の斜体変換


<?php
// この例では、preg_quote($word) を使って、アスタリスクが
// 正規表現での特殊な意味を帯びないようにしています

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

注意

注意: この関数はバイナリデータに対応しています。

preg_replace_callback

preg_match

Last updated: Fri, 03 Sep 2010

add a note User Contributed Notes
preg_quote

admin at nilamo dot com
04-Aug-2010 03:21


@zooly:



And what if $myvar = 'te\\E.t'?  It will match, when it shouldn't.  That's why you should use preg_quote().

zooly
21-Jul-2009 08:07


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

alexc223 at NOSPAM dot googlemail dot com
15-Jun-2009 07:41


Not sure why this note got deleted, but hey lets try again:



As of PHP 5.3, bug #47229 has been fixed and preg_quote *will* escape a hyphen (-). This may effect your code so ensure this is one thing you check when moving to 5.3.

frostschutz
20-Mar-2009 10:01


I wanted to escape a string of characters so I could match them in [], i.e. [.,-!"§$%\\\[\]\^].



Unfortunately preg_quote does not escape the - character which has a special meaning in [], i.e. [a-z].



So I used this hack: make - the delimiter of the expression, i.e.



preg_quote(userinput, "-")

preg_replace("-[$userinput]-u", "", $str)



Apparently using a special char as a delimiter of a regular expression disables this character, i.e. even if it's escaped it's not understood as special character for the expression anymore.



so the pattern "-[a\\-z]-u" matches the characters a, - and z, and not abc...xyz.



It would be nice if preg_quote also escaped characters that have special meanings even if they have this meaning only under certain conditions, such as inside [].

krishoog at gmail dot com
13-Oct-2008 02:51


To bizzigul at hotmail dot fr:

It's not a good practice to make somthing work *almost* all of the time. If the input contains a '`' you will still get an error. I recommend using the default delimiter ('/') and also feed this to preg_quote as second argument.

bizzigul at hotmail dot fr
30-Jul-2008 04:10


To prevent any problems, try to always use a delimiter that will *almost* not be used inside the regex, such as ` (back quote)





for example: instead of 


<?php preg_match('/foo\/bar\//',$somevar); ?>





use





<?php preg_match('`foo/bar/`',$somevar); ?>





it's that simple! like this, you won't have to bother with delimiters anymore...

Anonymous
26-Dec-2007 11:13


Wondering why your preg_replace fails, even if you have used preg_quote?



Try adding the delimiter / - preg_quote($string, '/');

add a note

preg_replace_callback

preg_match

Last updated: Fri, 03 Sep 2010