public function only($key)
    {
        $keys = is_array($key) ? $key : func_get_args();

        return new static($this->classname, $this->filterByKeys($keys));
    }
public function only($key)
    {
        $keys = is_array($key) ? $key : func_get_args();

        return new static($this->classname, $this->filterByKeys($keys));
    }
public function only ( $ key ) { $ keys = is_array ( $ key ) ? $ key : func_get_args ( ) ; return new static ( $ this -> classname , $ this -> filterByKeys ( $ keys ) ) ; }
Get all items with the specified keys.

@param mixed $key

@return static
Get all items with the specified keys .