Changing the error reporting level inside a scirpt useing the error_reporting() function does not work if @ is present before the function.

Ex.
(assuming php.ini has error_reporting set to E_ALL)

<?php
@error_reporting(E_ALL^E_NOTICE);
echo $a;
?>

Would still generate a warning about an undefined variable.

<?php
error_reporting(E_ALL^E_NOTICE);
echo $a;
?>

Works fine without any warnings.