If you cannot figure out the problem with your script from the error message, check these things first:

1. Look at the error_log file for your site, as it may have more information about the error.
2. Make sure the PHP file has at least read permissions (at least 644).
3. Make sure the file is owned by the administrative user's username and group.
4. You can also check out the main php site at http://php.net for information regarding the functions in your PHP script.