PHP extension pass an object as parameter

Hello i trie to port the PEAR HTML_Template_Sigma Class to an PHP extension. in the PHP Class are some callback functions registert $this->setCallbackFunction('e', array(&$this, '_htmlentities')); $this->setCallbackFunction('u', 'urlencode'); the easier callback's to a php function i managed with this code zval tplFunction; ZVAL_STRING(&tplFunction,"u"); zval callback; ZVAL_STRING(&callback,"urlencode"); zend_call_method_with_2_params ( obj,Template_Sigma, NULL, "setcallbackfunction", NULL, &tplFunction, &callback); but how can i pass the object from a private method of the PHP extension class to the setcallbackfunction as it is down in PHP with array(&$this, '_htmlentities') Best Regards Torsten