Fix weird unpack behaviour in DOM

ext/dom/dom_iterators.c

@@ -158,7 +158,7 @@ static void php_dom_iterator_current_key(zend_object_iterator *iter, zval *key)
 	zval *object = &iterator->intern.data;
 
 	if (instanceof_function(Z_OBJCE_P(object), dom_nodelist_class_entry)) {
-		ZVAL_LONG(key, iter->index);
+		ZVAL_LONG(key, iterator->index);
 	} else {
 		dom_object *intern = Z_DOMOBJ_P(&iterator->curobj);
 
@@ -189,6 +189,8 @@ static void php_dom_iterator_move_forward(zend_object_iterator *iter) /* {{{ */
 		return;
 	}
 
+	iterator->index++;
+
 	intern = Z_DOMOBJ_P(&iterator->curobj);
 	object = &iterator->intern.data;
 	nnmap = Z_DOMOBJ_P(object);
@@ -227,18 +229,18 @@ static void php_dom_iterator_move_forward(zend_object_iterator *iter) /* {{{ */
 							curnode = basenode->children;
 						}
 					} else {
-						previndex = iter->index - 1;
+						previndex = iterator->index - 1;
 						curnode = (xmlNodePtr)((php_libxml_node_ptr *)intern->ptr)->node;
 					}
 					curnode = dom_get_elements_by_tag_name_ns_raw(
-						basenode, curnode, (char *) objmap->ns, (char *) objmap->local, &previndex, iter->index);
+						basenode, curnode, (char *) objmap->ns, (char *) objmap->local, &previndex, iterator->index);
 				}
 			}
 		} else {
 			if (objmap->nodetype == XML_ENTITY_NODE) {
-				curnode = php_dom_libxml_hash_iter(objmap->ht, iter->index);
+				curnode = php_dom_libxml_hash_iter(objmap->ht, iterator->index);
 			} else {
-				curnode = php_dom_libxml_notation_iter(objmap->ht, iter->index);
+				curnode = php_dom_libxml_notation_iter(objmap->ht, iterator->index);
 			}
 		}
 	}

ext/dom/php_dom.h

@@ -98,6 +98,9 @@ typedef struct {
 	zend_object_iterator intern;
 	zval curobj;
 	HashPosition pos;
+	/* intern->index is only updated for FE_* opcodes, not for e.g. unpacking,
+	 * yet we need to track the position of the node relative to the start. */
+	zend_ulong index;
 	php_libxml_cache_tag cache_tag;
 } php_dom_iterator;
 

ext/dom/tests/unpack_foreach_behaviour.phpt

@@ -0,0 +1,31 @@
+--TEST--
+Unpacking vs foreach behaviour
+--EXTENSIONS--
+dom
+--FILE--
+<?php
+
+$dom = new DOMDocument;
+$dom->loadXML('<root><a/><b/></root>');
+
+echo "--- By foreach: ---\n";
+
+foreach ($dom->documentElement->getElementsByTagName('*') as $node) {
+    var_dump($node->localName);
+}
+
+echo "--- By unpacking: ---\n";
+
+$iter = $dom->documentElement->getElementsByTagName('*');
+foreach ([...$iter] as $node) {
+    var_dump($node->localName);
+}
+
+?>
+--EXPECT--
+--- By foreach: ---
+string(1) "a"
+string(1) "b"
+--- By unpacking: ---
+string(1) "a"
+string(1) "b"