Currently there's a bug from Plesk in which PHP error isn't shown. Please refer here - http://forum.parallels.com/showthread.php?t=259634
Basically it's for Plesk 10.4 but it also applies on the newer version which is the Plesk 11.
PHP error is not shown in error_log file. Regardless of what you put in “error_reporting” directive in php.ini or even in PHP settings from Plesk (eg. E_ALL & ~E_NOTICE). None of them work.
The work around is to use numberic values instead. For instance, in Plesk 11, there's a section for PHP settings (Subscriptions > tiberius-hk.com > Websites & Domains > your-domain.com *bottom part* > PHP settings). Under "error_reporting", key-in there the numberic value (eg. 6135 which is equivalent to E_ALL & ~E_NOTICE).
