PHP按字段分组

Question

我有三个类：Transport，ServiceStation，CatalogTransport：

$service1=new ServiceStation('Service1','Address1');
$service2=new ServiceStation('Service2','Address2');
$t1=new Transport("t1",'type1',100,'carcase1','engine1','chassis1',$service1);
$t2=new Transport("t2",'type2',200,'carcase2','engine2','chassis2',$service1);
$t3=new Transport("t3",'type3',300,'carcase3','engine3','chassis3',$service2);
$catalog=new CatalogTransport();
$catalog->addTransport($t1);
$catalog->addTransport($t2);
$catalog->addTransport($t3);
$catalog->showCatalog();

我的CatalogTranspot课程：

class CatalogTransport{
    private $catalog = [];
    public function addTransport(Transport $t) {
        $this->catalog[] = $t;
    }

    public function showCatalog() {
        echo '<pre>';
        print_r($this->catalog);
        echo '</pre>';
    }
}

我的showCatalog（）返回：

Array
(
     [0] => Transport Object
    (
        [name:Transport:private] => t1
        [type:Transport:private] => type1
        [weight:Transport:private] => 100
        [carcase:Transport:private] => carcase1
        [engine:Transport:private] => engine1
        [chassis:Transport:private] => chassis1
        [service:Transport:private] => ServiceStation Object
            (
                [name:ServiceStation:private] => Service1
                [address:ServiceStation:private] => Address1
            )

    )

[1] => Transport Object
    (
        [name:Transport:private] => t2
        [type:Transport:private] => type2
        [weight:Transport:private] => 200
        [carcase:Transport:private] => carcase2
        [engine:Transport:private] => engine2
        [chassis:Transport:private] => chassis2
        [service:Transport:private] => ServiceStation Object
            (
                [name:ServiceStation:private] => Service1
                [address:ServiceStation:private] => Address1
            )

    )

[2] => Transport Object
    (
        [name:Transport:private] => t3
        [type:Transport:private] => type3
        [weight:Transport:private] => 300
        [carcase:Transport:private] => carcase3
        [engine:Transport:private] => engine3
        [chassis:Transport:private] => chassis3
        [service:Transport:private] => ServiceStation Object
            (
                [name:ServiceStation:private] => Service2
                [address:ServiceStation:private] => Address2
            )

    )

)

如何通过现场服务对其进行分组？

我希望它会这样：

服务1：

T1，T2

服务2： t3

如何解决我的问题？