WordPress has quite a few hidden features. My favourite so far: MU Plugins, or “must-use plugins”. Introduced with WP 3.0, the code says:
/** * Check the mu-plugins directory and retrieve all mu-plugin files with any plugin data. * * WordPress only includes mu-plugin files in the base mu-plugins directory (wp-content/mu-plugins). * * @since 3.0.0 * @return array Key is the mu-plugin file path and the value is an array of the mu-plugin data. */
