BBcodes module not working
xbbcode maintainer here.

It seems that the module uses a Regex syntax that was introduced in PHP 5.2.2: http://php.net/manual/de/regexp.reference.subpatterns.php

I'll release a fix when I can; it's a pretty small code change: For each occurrence of (?&lt;...&gt; in the pattern, insert a P to make it (?P&lt;...&gt;.

Alternatively, you can fix it by upgrading to PHP 5.2.2 or later.

Edit: In fact, Drupal 7's minimum requirements mention PHP 5.2.5 (https://www.drupal.org/docs/7/system-requirements/overview).