<?phpclass dtc{ protected static $instance = null; public static function get_instance() { if(is_null(dtc::$instance)) dtc::$instance = new dtc(); return dtc::$instance; } protected $in_tx; protected $obj; protected function __construct() { $this->in_tx = false; $this->obj = array(); } public function in_tx() { return $this->in_tx; } public function register(transactable $obj) { $this->obj[] = $obj; } public function begin() { $this->in_tx = true; foreach($this->obj as $v) $v->begin(); } public function commit() { $this->in_tx = false; foreach($this->obj as $v) $v->commit(); } public function rollback() { $this->in_tx = false; foreach($this->obj as $v) $v->rollback(); }}interface transactable { public function begin(); public function commit(); public function rollback();}?>