php控制器，检查web根常量，在控制器中调用ajax还是直接？

Is this valid or a bad idea?

WEBROOT || define('WEBROOT', $config_file_setting);

BEFORE THE ABOVE IS USED...

My controller calls scripts which can also run independently (direct, outside of the controller) and runs pre-config.

Since my controller is called by htaccess at web root, do I even need the absolute path "WEBROOT"; I guess I could just rename it if needed?

case '/verify/':
case (preg_match('/\/verify\/([\d\w]{10,50})$/', $_SERVER['SCRIPT_URL']) ? true : false) :
    require(WEBROOT.'/controller-dir/verify.php');
    exit;

What about this one for ajax, good or bad idea?

    case (preg_match('/\/ajax\/([\w]{5,20})\.php$/', $_SERVER['SCRIPT_URL'], $filename) ? true : false) :
    require(WEBROOT.'/ajax-dir/'.$filename[1].'.php');
    exit;

Right now I am calling ajax scripts direct, but was considering putting it in the controller; secured better of course :)

I do the case preg_match's at the end of the switch, before default which becomes a 404 to avoid slowing valid & 301 redirects.

Thanks!