Disabling PHP notices to error.log

[Norman]

Hi

What is the recommended way to disable PHP notices to a clients error log?
I dont want to disable it for all clients , but just for specific site.

Any ideas?

[Wed Feb 20 17:56:38 2013] [warn] [client x.x.x.x] mod_fcgid: stderr: PHP Notice: Undefined index: account_id in /var/www/clients/clientX/webX/web/backend/system/commons.php on line 188, referer: http://X

The PHP scripts already contain <?php ini_set('display_errors', 0); ini_set("log_errors", 0); ini_set("error_reporting", null); error_reporting(0); session_start(); but they still seem to report notices.