public function __call($method, $parameters)
{
if (method_exists($this->_class_name, 'filter_' . $method)) {
array_unshift($parameters, $this);
return call_user_func_array(array($this->_class_name, 'filter_' . $method), $parameters);
} else {
throw new Exception(" no static {$method} found or static method 'filter_{$method}' not defined in " . $this->_class_name);
}
}