[Mooff]

Why are you using ob_start and ob_get_contents instead of file_get_contents or file?

I think it might be possible that you mess parts of the vbulletin php file up, if you use ob_end_clean in the wrong place? Not exactly sure if end_clean closed the last ob_start - or everything. And i do not think you need it if you use file() or file_get_contents() instead?

just realised you use a *.php file, then

$foo = include(YOURFILE); should have the desired effekt as long as your phpfile returns the desired value.