mysql - 請教關於PHP方法傳入參數的問題及依賴注入的適用場景?

<code class="php">$new  = new controllers\Order\NewOrder();
$new->setForm(new OrderFormData());
$new->sayForm();</code>

<code class="php">private $form;
public function setForm(\OrderFormData $example){
   $this->form = $example;
}
public function sayForm(){
    echo $this->form->say();
}
</code>

<code class="php">$new  = new controllers\Order\NewOrder();
$new->setForm(new OrderFormData());
$new->sayForm();</code>

<code class="php">private $form;
public function setForm(\OrderFormData $example){
   $this->form = $example;
}
public function sayForm(){
    echo $this->form->say();
}
</code>