laravel 依賴注入

<?php
/*依賴注入約束注入的類必需是實現visit接口的類*/
interface visit{
    public function go();

}
class car implements  visit{
    public function go(){
        echo '輪子跑';
    }
}
class train{
    public function go(){
        echo '動車組';
    }
}
class trive{
    public $visit;
    function __construct(visit $visit){//visit 接口的實現類
            $this->visit = $visit;
    }
    public function triveType(){
        $this->visit->go();
    }
}
$car = new car();
/*$trive = new trive($car); //旅行類注入轎車實例
$trive->triveType();   //輸出旅行方式

*/
$train = new train();
$trive = new trive($train); //旅行類注入火車實例
$trive->triveType();//報錯 因為注入的train實例沒有實現visit接口