How to turn on WordPress Error Reporting?
WP_DEBUG is a PHP constant,a global variable that can be used to trigger the “debug” mode throughout WordPress website. It’s default value is false and usually set to true in the wp-config.php file on development copies of wordpress website.
define( 'WP_DEBUG', true );
Note: The (true & false) values in the example are not surrounded by apostrophes (‘) because they are boolean values. If you set constants to ‘false’, they will be interpreted as true because the quotes make it a string rather than a boolean.