Let's take a look at that documentation. 0:00 The iterator interface requires five methods. 0:16 Current, key, next, rewind, and valid. 0:20 The countable interface requires a single count method. 0:30 Just like with our own interfaces, PHP will also throw exceptions 0:34 if we try to implement a built in interface without the required methods. 0:39 Since we are instantiating our collection class, 0:44 let's try previewing our site again. 0:46 We see the error telling us which methods need to be implemented. 0:51 So let's get to work. 0:55 For each public method we'll be creating, 0:57 we'll use a built-in function on our collection array. 0:59 For the iterator method, each function will be working with the array pointer. 1:02 The pointer saves the position on an array. 1:07 For public function current(), 1:09 we're going to return current 1:15 ($this->collection);. 1:21 This will return the current pointer of the collection array. 1:27 We can duplicate this method for other five methods. 1:31 For key, the function is called key(). 1:41 This gives you the key of the item the pointer is on. 1:49 For the method next, The function call is next. 1:54 For the method rewind((), The function call is actually reset. 2:07 This resets the pointer of the array to the first item. 2:18 For the method valid(), We're going to check the key 2:24 And see if it's not equal to null. 2:32 This will let us know if the current key is valid. 2:36 For count(), we'll us our common count function, 2:41 Which returns the number of items in the array. 2:48 Before we give our new collection a try, 2:50 lets add a vardump that will help us see what's going on. 2:52 In each of the iterator methods, we're going to add var_dump(_ _ and 2:56 then the magic constant METHOD. 3:02 Rewind, next key and 3:10 current. 3:16 We're ready to give our new collection a try. 3:19 So let's open index.php. 3:20 For our collection, we need to prse in the $repo. 3:22 By default, this will pull all the posts. 3:29 Let's loop through each post and return the title. 3:32 Foreach ($content as $item). 3:41 Echo $item-> title. 3:48 And let's check this out in the browser. 3:52 Let's view the source. 3:56 Let's increase this font size. 4:01 For the first pass, we can see that it rewinds the pointer. 4:07 Then it checks that the current item is valid. 4:12 If so, it returns the current item. 4:15 And this is where we get our title. 4:18 The following loops move the pointer to the next item 4:21 before checking that the item is valid and then returning current. 4:25 After the last item, the call to valid will return false and the loop will end. 4:31 Great, now that we've seen what happens, let's go back and 4:36 comment out those method dumps. 4:39