/**
* @param float $volume volume of backpack
* @param ItemsGroupInput[] $items array of items groups
*
* @return ItemsGroup
* @throws Exception
*/
function loadBag ($volume, $items)

<?php

class Item{

    /**
    * @var string name of item
    */

    private $name;

    /**
     * @var float volume of item
     */

    private $volume;

    /**
     * @var float price of item
     */

    private $price;

    /**
     * @var int count of items of such kinds
     */

    private $count;

    /**
     * @var ItemsGroup
     */

    private $group;

    /**
     * @return string
     */

    public function getName(){

        return $this->name;
    }

    /**
    * @return float
    */

    public function getVolume(){

        return $this->volume;
    }

    /**
     * @return float
     */

    public function getPrice(){

        return $this->price;
    }

    /**
     * @param ItemsGroup
     */

    public function setGroup(ItemsGroup $itemGroup){

        $this->group = $itemGroup;
    }

    /**
     * Item constructor
     * @param string $name
     * @param float $volume
     * @param float $price
     * @param int $count
     */

    function __construct($name, $volume, $price, $count){

        if(!is_string($name)){throw new exception('Item name should be a string!');} else{$this->name = $name;}
        if(!is_float($volume)){throw new exception('Item volume should be a float!');}else{$this->volume = $volume;}
        if(!is_float($price)){throw new exception('Item price should be a float!');}else{$this->price = $price;}
        if(!is_integer($count) || $count < 0){throw new exception('Item count should be an integer!');}else{$this->count = $count;}

    }

} // end of item class


class ItemsGroup{

    private static $idSeque = 1;

    /**
     * @var int
     */

    private $id;

    /**
     * @var Item[]
     */

    protected $items;

    public function __construct($items){

        $this->items = $items;
        $this->id = self::$idSeque;
        self::$idSeque++;
    }

    /**
     * @return Item[]
     */

    public function getItems(){

        return $this->items;
    }

    function addItem($item)
    {
        $this->items[] = $item;
    }

    public function getId(){

        return $this->id;
    }

    public function getTotalPrice(){

        $totalPrice = 0;

        foreach($this->getItems() as $item){

            $totalPrice+=$item->getPrice();
        }

        return $totalPrice;
    }
}

// end of itemGroup class

/**
 * @param float $volume volume of backpack
 * @param ItemsGroupInput[] $items array of items groups
 *
 *@return ItemsGroup
 *@throws Exception
 */

function loadBag($volume, $listOfItemGroup){

    $output = new itemsGroup(array());

    foreach($listOfItemGroup as $itemGroup){

        $items = $itemGroup->getItems();

    for($i = 0; $i < count($items); $i++){

            $output->addItem($items[$i]);

        }
    } // end of foreach

    return $output;

} // end of class


$hats = new ItemsGroup(

    array(

            new Item('hats1', 0.5, 1.99, 5),
            new Item('hats2', 0.3, 2.99, 2),
            new Item('hats3', 0.2, 1.50, 3)
    )
);


/* echo $hats->getId();

echo "<br>";

echo $hats->getTotalPrice(); */


$socks = new ItemsGroup(

    array(

            new Item('socks1', 0.01, 2.99, 2),
            new Item('socks2', 0.1, 3.99, 3),
            new Item('socks3', 0.02, 4.99, 4)
    )
);


/* echo "<br>";

echo $socks->getId();

echo "<br>";

echo $socks->getTotalPrice(); */


$tShirts = new ItemsGroup(
    array(
        new Item('t-shirt1', 0.1, 5.99, 4),
        new Item('t-shirt2', 0.1, 6.99, 5),
        new Item('t-shirt3', 0.15, 7.99, 6),
        new Item('t-shirt4', 0.2, 8.99, 7)
    )
);

/* echo "<br>";

echo $tShirts->getId();

echo "<br>";

echo $tShirts->getTotalPrice(); */

$pants = new ItemsGroup(
    array(
        new Item('pant1', 0.2, 5.99, 8),
        new Item('pant2', 0.21, 3.99, 4),
        new Item('pant3', 0.25, 2.99, 2)
    )
);

/* echo "<br>";

echo $pants->getId();

echo "<br>";

echo $pants->getTotalPrice(); */

///////////////////////////////////////////////////Call function///////////////////////////////////////////////////

try{

    echo "<pre>";
        print_r(loadBag(1, array($hats, $socks)));
    echo "</pre>";

} catch(Exception $e){

    echo "Caught exception: " . $e->getMessage();
}


?>