Pick a random plugin and add a test callback: // mod/resource/lib.php function mod_resource_before_session_start() { error_log("hello world"); } Purge caches: php admin/cli/purge_caches.php Tail the apache error log: tail -f /var/log/apache2/error.log Note: This may be in a different location depending on system. Load any page in Moodle Confirm that you see the string "hello world" in the error log Replace the call to error log with an exception: function mod_resource_before_session_start(){ throw new Exception('test'); } Reload the page Confirm that you there was an error shown on screen, and in the error log Confirm that the page still loaded as normal