Well I wasn't really sure where the issue was coming from. Now that I know that this may be a Phorum issue and not a problem on my server I'll troubleshoot some more to tease out the exact problem. Tried your search and the only hit I get is my post (i.e this thread).
That said, PHP 5.3 has been at end of life since June: [news.php.net]. Any potential security issues will not be fixed.
That said, PHP 5.3 has been at end of life since June: [news.php.net]. Any potential security issues will not be fixed.