In the event that you see the following error:
warning: preg_match: internal pcre_fullinfo() error -3 in /SERVER_PATH/includes/common.inc on line 592.
Be aware that this issue exists at the server level, outside of Drupal code. Put plainly, the error means that the server's PCRE (Perl Compatible Regular Expression) library is not configured correctly.
This error may be caused any time a Drupal module calls a PCRE function. Typically, the error appears within common.inc, but this is not always the case.
Depending on the server environment, there are several different causes (including a reported bug in some versions of PHP 5).
This manual page is designed to capture known instances of this bug,
- An upgrade of RedHat included a bad library and required a patch. (Details to follow)
- Send the content of the error to your system admin and have them debug your PHP's PCRE module.