fix bug #73471 PHP freezes with AppendIterator

NEWS

@@ -6,6 +6,9 @@ PHP                                                                        NEWS
   . Fixed bug #74780 (parse_url() borken when query string contains colon). 
     (jhdxr)
 
+- SPL:
+  . Fixed bug #73471 (PHP freezes with AppendIterator). (jhdxr)
+
 06 Jul 2017 PHP 7.0.21
 
 - Core:

ext/spl/spl_iterators.c

@@ -3383,7 +3383,12 @@ SPL_METHOD(AppendIterator, append)
 	if (zend_parse_parameters_ex(ZEND_PARSE_PARAMS_QUIET, ZEND_NUM_ARGS(), "O", &it, zend_ce_iterator) == FAILURE) {
 		return;
 	}
-	spl_array_iterator_append(&intern->u.append.zarrayit, it);
+	if (intern->u.append.iterator->funcs->valid(intern->u.append.iterator) == SUCCESS) {
+		spl_array_iterator_append(&intern->u.append.zarrayit, it);
+		intern->u.append.iterator->funcs->move_forward(intern->u.append.iterator);
+	}else{
+		spl_array_iterator_append(&intern->u.append.zarrayit, it);
+	}
 
 	if (!intern->inner.iterator || spl_dual_it_valid(intern) != SUCCESS) {
 		if (intern->u.append.iterator->funcs->valid(intern->u.append.iterator) != SUCCESS) {

ext/spl/tests/bug73471.phpt

@@ -0,0 +1,15 @@
+--TEST--
+Bug #73471 PHP freezes with AppendIterator
+--FILE--
+<?php
+
+$iterator = new \AppendIterator();
+$events = new \ArrayIterator([1,2,3,4,5]);
+$events2 = new \ArrayIterator(['a', 'b', 'c']);
+$iterator->append($events);
+foreach($events as $event){}
+$iterator->append($events2);
+?>
+===DONE===
+--EXPECT--	
+===DONE===