public static function fromArray(array $array, $unit = 'px')
    {
        // Requirements for given array:
        // - indexes "0" and "1"
        // - should contains exactly 2 elements
        if (
            array_key_exists(0, $array)
            && array_key_exists(1, $array)
            && 2 === count($array)
        ) {
            list($width, $height) = $array;

            return new self($width, $height, $unit);
        }

        return null;
    }