preg_quote

(PHP 4, PHP 5)

preg_quote — 转义正则表达式字符

说明

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

preg_quote()需要参数str并向其中每个正则表达式语法中的字符前增加一个反斜线. 这通常用于你有一些运行时字符串需要作为正则表达式进行匹配的时候.

正则表达式特殊字符有: . \ + * ? [ ^ ] $ ( ) { } = ! < > | : -

参数

str: 输入字符串
delimiter: 如果指定了可选参数delimiter, 它也会被转义. 这通常用于转义PCRE函数使用的分隔符. /是最通用的分隔符.

返回值

返回转义后的字符串.

更新日志

版本	说明
5.3.0	字符-被增加为需要转义的.

范例

Example #1 preg_quote()示例


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

Example #2 将文本中的单词替换为斜体


<?php
//在这个例子中, preg_quote($word)用于保持星号原文涵义, 使其不使用正则表达式中的特殊语义.

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

注释

Note: 此函数可安全用于二进制对象。

preg_replace_callback

preg_match

[edit] Last updated: Fri, 25 May 2012

add a note User Contributed Notes preg_quote

billadoid at gmail dot com 12-Jan-2012 05:11


If you need to quote everything but a wildcard, maybe this function will come handy to you:





<?php


protected function _ruleOptionIsMatched($option, $subject)


{


    $option = preg_quote($option, '#');


    $option = str_replace('\*', '.*', $option);





    if(preg_match("#^$option$#", $subject))


    {


        return true;


    }


    else


    {


        return false;


    }


}


?>

admin at nilamo dot com 04-Aug-2010 08:21


@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 01:07


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 12:41


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 02:01


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 07:51


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 09:10


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 03:13


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



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

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