Douglas Brown has posted some hints to help you find errors in your PHP scripts all centered around error reporting settings.

There are several methods to solve errors in PHP code. Sometimes when the user waits to see an output a blank page will be shown if there is an error. To show the errors E_ALL^E_STRICT is used for the PHP 5 version. Contrarily, remaining versions just use E_ALL.

He talks about the log_errors and display_errors settings in your php.ini, the error_reporting function call or a custom error handler as shown in this example from the PHP manual.