This question has been answered by markh. See the first response.
<?php
error_reporting(E_ALL);
ini_set('display_errors', 1);It depends on how it's turned off, but often (not always) putting this in the top of the root index.php works great:
<!--?php error_reporting(E_ALL); ini_set('display_errors', 1);
On some servers they may also be logging php errors to a central error.log file (perhaps under a /var/log/ directory, or a logs directory above public_html) or have logs available from the control panel. -->