Mine

//file cp.phpclass cp {	...		function get_id_cp() {		return $this->id_cp;	}...}//file zone.phpclass zone {..function get_id_zone() {		return $this->id_zone;	}...}//file zone_cp.phpclass zone_cp {		var $cp;	var $zone;		function zone_cp($zone,$cp) {		global $zone,$cp;		$this->setZone($zone);		$this->setCp($cp);		print_r($this);		echo dirname(__FILE__);		$this->print_();	}function print_() {		echo $this->zone->get_id_zone(); //error here : Call to a member function on a non-object	}	...}