how to return an array of c++ objects

I have a Graph object which contains a std::Map<int, Node*> nodes . graph->getNodes() just returns this->nodes . It is this function I'm attempting to wrap in a PHP extension. I have already exposed the Graph and Node objects to userspace and need to return an array of Node objects. However, I'm getting a segfault with my current code and can't figure out why. Can someone spot my mistake? Here's the relevant code (please let me know if I forget something useful): ---code--- struct node_object { zend_object std; Node *node; }; zend_class_entry *node_ce; /* snip... */ PHP_METHOD(Graph, getNodes) { Graph *graph; graph_object *obj = (graph_object*)zend_object_store_get_object(getThis() TSRMLS_CC); graph = obj->graph; node_object* n; zval* node_zval; if (obj == NULL) { RETURN_NULL(); } if (object_init_ex(node_zval, node_ce) != SUCCESS) { RETURN_NULL(); } std::map<int, Node*> nodes = graph->getNodes(); array_init(return_value); for (std::map<int, Node*>::iterator i = nodes.begin(); i != nodes.end(); ++i) { php_printf("X"); n = (node_object*) zend_object_store_get_object(node_zval TSRMLS_CC); n->node = i->second; add_index_zval(return_value, i->first, node_zval); } php_printf("]"); } --- end code --- --- output --- $ php -r '$g = new Graph(); $g->getNodes();' XX]Segmentation fault --- end output --- (As you can see, the two-node long map is being traversed, the function exits, then the segfault.) Thanks very much for your help. John