Does arguments order in constructor matters?

Question

I've noticed strange situation while creating class contructor (__construct).

Here is my code:

public function __construct(
        \Magento\Framework\Model\Context $context,
        \Magento\Framework\Registry $registry,
        \Magento\Framework\Api\ExtensionAttributesFactory $extensionFactory,
        \Magento\Framework\Api\AttributeValueFactory $customAttributeFactory,
        \Magento\Store\Model\StoreManagerInterface $storeManager,
        \Magento\Framework\Model\ResourceModel\AbstractResource $resource = null,
        \Magento\Framework\Data\Collection\AbstractDb $resourceCollection = null,
        \Magento\Catalog\Model\ResourceModel\Product\Collection $productCollection,
        array $data = []
    )

And:

public function __construct(
        \Magento\Catalog\Model\ResourceModel\Product\Collection $productCollection,
        \Magento\Framework\Model\Context $context,
        \Magento\Framework\Registry $registry,
        \Magento\Framework\Api\ExtensionAttributesFactory $extensionFactory,
        \Magento\Framework\Api\AttributeValueFactory $customAttributeFactory,
        \Magento\Store\Model\StoreManagerInterface $storeManager,
        \Magento\Framework\Model\ResourceModel\AbstractResource $resource = null,
        \Magento\Framework\Data\Collection\AbstractDb $resourceCollection = null,
        array $data = []
    )

In first case it returns Internal Server Error 500, but in second case all works fine.

Why does agruments order affects?

Thanks in advance!

Answer 1

Optional parameters MUST be going after the required.

If you omit this rule your code will depend on concrete implementation, because you need to know all default values for optional parameters that can be different in other implementations. This breaks Liskov substitution principle.

It's why the first example does not work.