public static function invert(array $array)
	{
		$return = array();

		foreach ($array as $base => $values)
		{
			if (!\is_array($values))
			{
				continue;
			}

			foreach ($values as $key)
			{
				// If the key isn't scalar then ignore it.
				if (is_scalar($key))
				{
					$return[$key] = $base;
				}
			}
		}

		return $return;
	}