Merge pull request #190 from Masterminds/mitigate-cyclic-refs

mitigate cyclic reference between output rules and the traverser objects

src/HTML5.php

@@ -212,7 +212,10 @@ public function save($dom, $file, $options = array())
         $trav = new Traverser($dom, $stream, $rules, $options);
 
         $trav->walk();
-
+        /*
+         * release the traverser to avoid cyclic references and allow PHP to free memory without waiting for gc_collect_cycles
+         */
+        $rules->unsetTraverser();
         if ($close) {
             fclose($stream);
         }

src/HTML5/Serializer/OutputRules.php

@@ -182,6 +182,13 @@ public function setTraverser(Traverser $traverser)
         return $this;
     }
 
+    public function unsetTraverser()
+    {
+        $this->traverser = null;
+
+        return $this;
+    }
+
     public function document($dom)
     {
         $this->doctype();