DDC-737 - Implemented slice() on PersistentCollection for fowards compatibility reasons. The method will be required on Collection interface with the next Doctrine\Common release

lib/Doctrine/ORM/PersistentCollection.php

@@ -661,4 +661,21 @@ final class PersistentCollection implements Collection
     {
         return $this->coll;
     }
+
+    /**
+     * Extract a slice of $length elements starting at position $offset from the Collection.
+     *
+     * If $length is null it returns all elements from $offset to the end of the Collection.
+     * Keys have to be preserved by this method. Calling this method will only return the
+     * selected slice and NOT change the elements contained in the collection slice is called on.
+     *
+     * @param int $offset
+     * @param int $length
+     * @return array
+     */
+    public function slice($offset, $length = null)
+    {
+        $this->initialize();
+        return $this->coll->slice($offset, $length);
+    }
 }