WordPress have a debug mode which allow you to easily get information when something goes wrong. To enable the debug mode, you have to add a constant to the wp-config.php file. But what about an easy way to switch on the debug mode, even without accessing wp-config.php?
The first thing to do is to add the following code to your wp-config.php file. This file is located at the root of your WordPress install.
if ( isset($_GET['debug']) && $_GET['debug'] == 'debug') define('WP_DEBUG', true);
Once done, simply add a GET parameter to the url of the page you’d like to debug, as shown below:
Thanks to Joost de Valk for this great tip!