public function output()
    {
        if (!file_exists($this->_file))
            throw new RuntimeException(
                "Error loading template file: $this->_file.", 
                1
            );

        $output = file_get_contents($this->_file);
        
        foreach ($this->_vars as $key => $value) {
            $tagToReplace = "[@$key]";
            $output = str_replace($tagToReplace, $value, $output);
        }

        return $output;
    }