php.net |  support |  documentation |  report a bug |  advanced search |  search howto |  statistics |  random bug |  login

go to bug id or search bugs for

Bug #62646 Impossible to escape/match delimiters within \Q \E
Submitted: 2012-07-24 00:33 UTC Modified: 2012-07-24 01:55 UTC
From: Andreas dot Klauer at metamorpher dot de Assigned:
Status: Not a bug Package: PCRE related
PHP Version: 5.3.15 OS:
Private report: No CVE-ID: None
View Developer Edit
Welcome back! If you're the original bug submitter, here's where you can edit the bug or add additional notes.
If you forgot your password, you can retrieve your password here.
Password:
Status:
Package:
Bug Type:
Summary:
From: Andreas dot Klauer at metamorpher dot de
New email:
PHP Version: OS:

 

 [2012-07-24 00:33 UTC] Andreas dot Klauer at metamorpher dot de 
Description:
------------
PCRE allows literal matches of strings between \Q and \E. This is also documented, \Q.$.\E will match literal .$.

However, if that literal string contains the regexp delimiter (/ or # or ~ or () or whichever you choose), the regexp compile either fails, or the match fails because it tries to match the escape char used to escape the delimiter.

The problem is php_pcre::pcre_get_compiled_regex_cache() which parses the delimiter, not taking \Q \E in account. Delimiters between \Q \E should be treated as literal characters, not delimiters (that's what Perl does); or alternatively if delimiters have to be escaped, the escape char should be removed from the pattern.

Workaround: Use preg_quote() instead of \Q \E if there's a chance the delimiter may appear within \Q \E

Test script:
---------------
preg_replace("/\Q/#~\E/", ...);
=> Warning: preg_replace(): Unknown modifier '#' in php shell code on line 1

preg_replace("/\Q\/#~\E/", "OK", "/#~");
=> "/#~" (expected "OK")

preg_replace("/\Q\/#~\E/", "FAIL", "\/#~")
=> "FAIL" (expected "\/#~");

Patches

Pull Requests

History

AllCommentsChangesGit/SVN commitsRelated reports
 [2012-07-24 01:55 UTC] felipe@php.net
-Status: Open +Status: Not a bug
 [2012-07-24 01:55 UTC] felipe@php.net 
Thank you for taking the time to write to us, but this is not
a bug. Please double-check the documentation available at
http://www.php.net/manual/ and the instructions on how to report
a bug at http://bugs.php.net/how-to-report.php

Hi, the pcretest tool doesn't even handle the \Q..\E stuff as you mentioned. It works just like the [..] one. And using Perl I did to escape the delimiter inside \Q..\E.
 [2012-07-24 08:30 UTC] Andreas dot Klauer at metamorpher dot de 
But even if you escape the delimiter, it's not possible to match literal /#~ if one of those is the delimiter; you have to escape it, but if you do escape it, it matches literal \/#~ instead of just /#~.

Perl:
$subject = "foo/#~bar";
$subject =~ s/\Q\/#~\E/baz/;
print $subject;
=> "foobazbar"

PHP:
$subject = "foo/#~bar";
$subject = preg_replace("/\Q\/#~\E/", "baz", $subject);
echo $subject;
=> "foo/#~bar"

PHP tries to match literal \/#~ here.
 
PHP Copyright © 2001-2025 The PHP Group
All rights reserved. 		Last updated: Thu Jul 03 15:01:34 2025 UTC