Req #51777 [Opn]: RegEx matching fails
Edit report at http://bugs.php.net/bug.php?id=51777&edit=1
ID: 51777
User updated by: trevor at ridgebizdev dot com
Reported by: trevor at ridgebizdev dot com
Summary: RegEx matching fails
Status: Open
Type: Feature/Change Request
Package: PCRE related
Operating System: Windows XP
PHP Version: 5.3.2
New Comment:
Setting the pcre.backtrack_limit makes 51777 an installation feature
request; however, because no warning is fired, the report remains a bug.
Previous Comments:
------------------------------------------------------------------------
[2010-05-12 20:10:54] trevor at ridgebizdev dot com
[Pcre]
;PCRE library backtracking limit.
; http://php.net/pcre.backtrack-limit
;pcre.backtrack_limit=100000
;PCRE library recursion limit.
;Please note that if you set this value to a high number you may consume
all
;the available process stack and eventually crash PHP (due to reaching
the
;stack size limit imposed by the Operating System).
; http://php.net/pcre.recursion-limit
;pcre.recursion_limit=100000
I have nothing set (I must be using the default). I use Windows XP
Professional with 4GB RAM and Core2Duo.
------------------------------------------------------------------------
[2010-05-12 09:14:13] mike@php.net
Please try using this snapshot:
http://snaps.php.net/php5.3-latest.tar.gz
For Windows:
http://windows.php.net/snapshots/
Works here. Do you have a pcre.backtrack_limit set?
------------------------------------------------------------------------
[2010-05-09 18:36:54] trevor at ridgebizdev dot com
Description:
------------
When a RegEx "looks" over ~32768 times during a successful match, every
RegEx function fails and returns the empty string.
Test script:
---------------
<?php
$response = http_get("http://www.travelocity.com");
// no problem with these first 2 RegExs
$response2 = preg_replace('/\s+/'," ",$response);
$mytitle =
preg_replace('/.*?<\s*title\s*>([^<]*)<.*/i','${1}',$response2);
echo "\nTitle Match Forward: ".$mytitle."\n\n";
// now, here's a problem
$mytitle2 =
preg_replace('/.*<\s*title\s*>([^<]*)<.*/i','${1}',$response2);
echo "\nTitle Match Backward: ".$mytitle2."\n\n";
?>
Expected result:
----------------
$mytitle gets extracted properly and echoed because the RegEx never
looks more than 32768 times starting at the beginning of the
travelocity.com page source. $mytitle2 never gets extracted because the
RegEx looks more than 32768 times successfully and preg_replace()
crashes into the empty string. Matching forward for the title is
working; matching backward for the title is failing for large buffers.
Actual result:
--------------
Title Match Forward: Travelocity Travel: Airline Tickets, Hotels,
Flights, Vacations, Cruises & Car Rentals
Title Match Backward:
------------------------------------------------------------------------
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Edit this bug report at http://bugs.php.net/bug.php?id=51777&edit=1
Thread (7 messages)