Iterator pattern added

Iterator/Iterator.php

@@ -0,0 +1,81 @@
+<?php
+
+class Book
+{
+    private $title;
+
+    public function __construct($title)
+    {
+        $this->title = $title;
+    }
+
+    public function getTitle()
+    {
+        return $this->title;
+    }
+}
+
+class BookList implements Iterator, Countable
+{
+    private $books = [];
+
+    private $currentIndex = 0;
+
+    public function current()
+    {
+        return $this->books[$this->currentIndex];
+    }
+
+    public function key()
+    {
+        return $this->currentIndex;
+    }
+
+    public function next()
+    {
+        $this->currentIndex++;
+    }
+
+    public function rewind()
+    {
+        $this->currentIndex = 0;
+    }
+
+    public function valid()
+    {
+        return isset($this->books[$this->currentIndex]);
+    }
+
+    public function count()
+    {
+        return count($this->books);
+    }
+
+    public function addBook(Book $book)
+    {
+        $this->books[] = $book;
+    }
+
+    public function removeBook(Book $bookToRemove)
+    {
+        foreach ($this->books as $key => $book) {
+            if ($book->getTitle() === $bookToRemove->getTitle()) {
+                unset($this->books[$key]);
+            }
+        }
+
+        $this->books = array_values($this->books);
+    }
+}
+
+$bookList = new BookList();
+$bookList->addBook(new Book('Design Pattern'));
+$bookList->addBook(new Book('Head First Design Pattern'));
+$bookList->addBook(new Book('Clean Code'));
+$bookList->addBook(new Book('The Pragmatic Programmer'));
+
+$bookList->removeBook(new Book('Design Pattern'));
+
+foreach ($bookList as $book) {
+    echo $book->getTitle() . PHP_EOL;
+}