[MUSIC] 0:00 Now that we have some data to work with, we want to create a collection that we can 0:05 use for loops and perform some additional functionalities. 0:09 For the looping capabilities, PHP offers us an iterator interface, so 0:13 we don't need to create our own. 0:18 Often, when working with interfaces, 0:22 you will use existing interfaces such as the iterator. 0:23 Besides the interfaces that are built into PHP, 0:28 most frameworks include their own interfaces. 0:32 These interfaces work as a kind of guaranteed documentation for 0:35 using individual components. 0:39 By combining multiple interfaces, we can build powerful components 0:41 that can be easily understood by the rest of our application. 0:46 Let's go back into our collection file. 0:50 We are going to use implements Iterator. 0:52 This implements the built in iterator interface. 0:57 This implements keyword is how we specify that our class 1:01 will meet the contract of a given interface. 1:06 We add the name of the interface and 1:09 then it's up to us to implement the details of that interface's methods. 1:11 Somewhere in this class, I mentioned that we can combine interfaces together 1:16 to give our class more and more capabilities. 1:20 We can do that by adding more interface names separated by comma. 1:24 So for this example, we also want the collection to be countable, so 1:28 we can add a comma and then the built-in Countable. 1:33 We'll use two properties, 1:36 protected $repo; and a public $collection;. 1:39 Then we'll set up a construct. 1:48 On construct, we're going to pass the $repo and 1:50 optionally the ID and field if we want to limit our collection. 1:53 We don't care where the data is coming from, but we do need to know that we can 1:58 access the find and all methods that we set up in our repository interface. 2:02 Type declarations, also called type hinting, 2:08 allows us to require a specific type of parameter on a method call. 2:11 Type hinting for classes and 2:16 interfaces was added in PHP5 along with arrays and callable. 2:18 PHP7 added scaler type hints. 2:22 These are the basic variable types of Boolean, float, integer and string. 2:25 To specify that our first parameter must 2:30 implement the repository interface, 2:35 we specify the name of the interface before the parameter, 2:40 public function __construct( 2:47 RepositoryInterface, and then $repo, 2:51 then we can add our optional parameters, 2:56 $id = null, $field = 'id'). 3:01 On construct, we first set the local $repo, 3:06 then we populate our collection $this -> repo = $repo; if the ID is not empty. 3:11 Then we're going to say $this -> 3:23 collection = $this->repo-> find(. 3:28 We're going to past posts, 3:35 the ID and the field. 3:40 Else. 3:44 $this->collection = $this-> 3:47 repo->all('posts');. 3:54 Now we need to implement the methods from the iterator and countable interfaces. 4:00