Как определить долгий авиамаршрут?

$Longest_Path = new CLongestPathBuilder($routes); // создаем экземпляр класса
$Longest_Path -> printLongestPath(); // выводим информацию о самом долгом маршруте



Class CLongestPathBuilder
{
	protected $arResult = [];
	protected $iterator = 0;

	function __construct($routes)
	{
		// Sorting routes array by date (dt_start field)
		try
		{
			$this->arResult['routes'] = CExtraTools::sortArrayByDate($routes);
		}
		catch(Exception $e)
		{
			echo $e->GetMessage();
			exit(1);
		}

		foreach($this->arResult['routes'] as $route)
		{
			$this->arResult['path'][$this->iterator]['full_path'] .= $route['start'].' -> '.$route['finish'];
			$this->arResult['path'][$this->iterator]['routes_count'] = 1; 
			// Trying to find all available routes from last destination ($route['finish'])
			$this->getRoutes($route);
			$this->iterator++;
		}
	}

	protected function getRoutes($route1)
	{
		// Get available routes from last destination
		if(!$this->arResult['path'][$this->iterator]['prev_date'])
		{
			$this->arResult['path'][$this->iterator]['prev_date'] = $route1['dt_start'];
		}
		foreach($this->arResult['routes'] as $route2) 
		{
			if( ($route1['start'] != $route2['start']) && ($route1['finish'] == $route2['start']) && ($this->arResult['path'][$this->iterator]['prev_date'] < $route2['dt_start']) )
			{
				$this->arResult['path'][$this->iterator]['full_path'] .= ' -> '.$route2['finish'];
				$this->arResult['path'][$this->iterator]['days'] += CExtraTools::diffDates($route1['dt_start'], $route2['dt_start']);
				$this->arResult['path'][$this->iterator]['dates'][] = $route1['dt_start'].' - '.$route2['dt_start'];
				$this->arResult['path'][$this->iterator]['prev_date'] = $route2['dt_start'];
				$this->arResult['path'][$this->iterator]['routes_count']++; // Number of routes in the path
				$this->setLongest($this->arResult['path'][$this->iterator]['days']); // Setting current path as the longest one
				$this->getRoutes($route2);
			}
		}
	}

	protected function setLongest($duration)
	{
		// a function used to set longest path
		if($duration > $this->arResult['longest_path']['days'])
		{
			$this->arResult['longest_path'] = $this->arResult['path'][$this->iterator];
		}
	}

	public function getLongest()
	{
		// a function used to get longest path
		return $this->arResult['longest_path'];
	}

	public function getPaths()
	{
		// a function used to get longest path
		return $this->arResult['path'];
	}

	public function printAllPaths()
	{
		CExtraTools::pre($this->arResult['path']);
	}

	public function printLongestPath()
	{
		CExtraTools::pre($this->arResult['longest_path']);
	}
}



Class CExtraTools
{
	public static function diffDates($date1, $date2)
	{
		// The function to count the difference between two dates
		try
		{
			$datetime1 = new DateTime($date1);
			$datetime2 = new DateTime($date2);
		}
		catch (Exception $e) {
			echo $e->getMessage();
			exit(1);
		}
		$interval = $datetime1->diff($datetime2);
		return $interval->invert ? $interval->days*(-1) : $interval->days;
	}

	public static function pre($var)
	{
		// modification of print_r method
		echo '<pre>';
		print_r($var);
		echo '</pre>';
	}

	protected static function cmp($a, $b)
	{
		// only to sort array in sortArrayByDate() function
		if ($a['dt_start'] == $b['dt_start']) {
			return 0;
		}
		return ($a['dt_start'] < $b['dt_start']) ? -1 : 1;
	}

	public static function sortArrayByDate($array)
	{
		// Sort array by date (dt_start field)
		if(!is_array($array))
		{
			throw new Exception('Должен быть передан массив');
		}
		usort($array, "self::cmp");
		return $array;
	}
}