When troubleshooting PHP errors, you will want to review your PHP logs. If you don't have PHP logs to review, use the following process to set up logging:

You should always backup your site before making any changes to your site. Locate your PHP initialization file. Edit the file. Place the following line in your initialization file:

        error_log = /path/to/your/webroot/php_error.log

error_log is the PHP function that will tell the web server to output your logs to a new file.

"/path/to/your/webroot/php_error.log" is the path to your new log.

Make sure to replace /path/to/your/webroot with the actual path your hosting account uses.

Create the a file named php_error.log in the in the webroot of your hosting. Restart your PHP processes.

Next Steps:

Review your php_error.log for error details.

More info:

For more information about PHP error logs, visit PHP.net.