public static function allKeys()
    {
        static $allKeys = null;

        if (is_null($allKeys)) {
            $allKeys = array_values((new ReflectionClass(get_called_class()))->getConstants());
        }

        return $allKeys;
    }
public static function allKeys()
    {
        static $allKeys = null;

        if (is_null($allKeys)) {
            $allKeys = array_values((new ReflectionClass(get_called_class()))->getConstants());
        }

        return $allKeys;
    }
public static function allKeys ( ) { static $ allKeys = null ; if ( is_null ( $ allKeys ) ) { $ allKeys = array_values ( ( new ReflectionClass ( get_called_class ( ) ) ) -> getConstants ( ) ) ; } return $ allKeys ; }
Get the all possible keys.

@return string[]
Get the all possible keys .