Yes. Introduced in WordPress 2.3.1, WP_DEBUG is a constant that helps developers debug code, which could be a theme or plugin. By default, WP_DEBUG is set to false on our main network, but we also maintain a more developer-friendly network, where WP_DEBUG is set to true. In addition, that network has a number of plugins to assist developers, including: Debug Bar Debug Bar Slow Actions Query Monitor Debug Bar Cron Debug Bar Extender Debug Bar Super Globals For subscribers currently paying on either [wpp_plans plan=\\"3\\"] or [wpp_plans plan=\\"4\\"], upon your support request we'll create a new site or a copy of an existing site (your choice) on our developer-friendly network.