It might be helpful to know what PCRE configuration limits may be
assigned in the PHP.INI file for vBulletin.
[Pcre]
pcre.backtrack_limit=100000
pcre.recursion_limit=100000
The "backtrack_limit" corresponds to PCRE's "match_limit".
The PHP default may be 100000 for each. PHP should be responding with
an HTTP 500 error status when one of the PCRE limits is reached.
However, the IE browser defaults to "Show friendly HTTP error messages"
and the particular text associated with the 500 error status is hidden
from view. Knowing the particulars of a PHP exception and its HTTP
response could be beneficial.
If PCRE's execution of that expression reaches a higher match limit
in version 8.21 than in 8.20 (I don't know if it would or not), then
raising the PHP backtrack_limit may resolve the issue.
http://php.net/manual/en/pcre.configuration.php
Regards,
Graycode
