Behavioral\Iterator restructured

Behavioral/Iterator/BookListReverseIterator.php

@@ -0,0 +1,23 @@
+<?php
+
+namespace DesignPatterns\Behavioral\Iterator;
+
+class BookListReverseIterator extends BookListIterator
+{
+
+    public function __construct(BookList $bookList)
+    {
+        $this->bookList = $bookList;
+        $this->currentBook = $this->bookList->count() - 1;
+    }
+
+    public function next()
+    {
+        $this->currentBook--;
+    }
+
+    public function valid()
+    {
+        return 0 <= $this->currentBook;
+    }
+}