PHPWarrior\Abilities\Base::verify_direction PHP Method

    public function verify_direction($direction)
    {
        $direction = \PHPWarrior\Position::normalize_direction($direction);
        if (array_search($direction, \PHPWarrior\Position::$RELATIVE_DIRECTIONS) === false) {
            throw new \Exception("Unknown direction {$direction}. Should be :forward, :backward, :left or :right.");
        }
    }