Phx and Parser limits - My Forums

Re: Phx and Parser limits

megab — Aug 26, 2010, 10:38 AM

The PCRE backtrack limit was causing PHx code to show on my Maxigallery when I had over 100 pictures. This did "fix" the problem.

You can also set [tt]php_value pcre.backtrack_limit 16000000[/tt] in your .htaccess file in many cases, instead of modifying the code. It could affect more of the site if there are many bad regular expression call that should "time out" sooner.

Re: Phx and Parser limits

mrhaw — Jan 03, 2010, 03:22 PM

Sweet!

Re: Phx and Parser limits

coroico — Nov 25, 2009, 10:31 AM

Thanks Mike. I spend some hours with Xdebug to undertsand and identify where the problem is. But I am happy with the results now.

Re: Phx and Parser limits

pixelchutes — Nov 25, 2009, 10:14 AM

Quote from: pixelchutes at Nov 24, 2009, 06:53 AM

Great find, coroico! Thank you for your input, PMS. This definitely helps clarify things for me on my end. Will try increasing the limit on some currently impacted sites and post-back with the results.

So awesome! This totally fixed any PHx limitation I was previously running into. By updating the PCRE backlimit configuration in the php.ini, all of my sites that were previously impacted have inherently been fixed. Plenty to be thankful for this Thanksgiving

Re: Phx and Parser limits

pixelchutes — Nov 24, 2009, 12:53 AM

Great find, coroico! Thank you for your input, PMS. This definitely helps clarify things for me on my end. Will try increasing the limit on some currently impacted sites and post-back with the results.

Re: Phx and Parser limits

PaulSuckling — Nov 23, 2009, 03:19 AM

No. As I understand it the backtrack_limit setting sets the maximum number of bytes preg is allowed to search over before it gives up. The strings I’m searching are never as big as 10MB however. Most document templates/web pages are smaller than 1 MB. This setting just guarantees that preg will search the whole string before giving up - which is what I wanted in this case.

Re: Phx and Parser limits

coroico — Nov 23, 2009, 03:11 AM

ini_set('pcre.backtrack_limit', '16000000');

Do you know the corresponding size allowed with this value ? If my assumptions are correct = 64 * 16000000 / 100000 / 1024 = 10 Mb !

With this value, you haven’t memory bottleneck during the script execution ?

Re: Phx and Parser limits

PaulSuckling — Nov 22, 2009, 05:08 PM

Just noticed this thread by chance. I too have come across this problem and ended up having to increase the backtrack limit size when parsing multilingual document templates within YAMS. (These can be approx. n times the size of normal document templates, where n is the number of languages.) I was wondering how big I would need to make the backtrack limit to be sure to avoid problems. I ended up using:

ini_set('pcre.backtrack_limit', '16000000');

within the code. This is approximately the maximum number of single byte characters that are allowed in the MODx content field. Although the number is very large I haven’t encountered any negative side-effects.

Re: Phx and Parser limits

zaigham — Nov 19, 2009, 06:25 PM

Nice find coroico.

Now we know whats happening behind the scenes.

Thanks

Re: Phx and Parser limits

coroico — Nov 19, 2009, 05:59 PM

Just of out curiosity, in my php_init file,I have doubled the value of the pcre.bactrack_limit. From 100000 to 200000.

;PCRE library backtracking limit.
pcre.backtrack_limit=200000

With this value, now I could display 512 lignes instead of 256

As one UTF-8 character is encoded on 2 bytes, the correct size limit with the default value of 100000 for the pcre.backtrack_limit is 256*128*2 = 64kb rather than 32kb.

About pcre.backtrack_limit : http://bugs.php.net/bug.php?id=40846