public function exists($table, $column = null)
    {
        $rule = $table;

        // Take any argument after the 2 defined ones
        $args = array_slice(func_get_args(), 2);

        if (isset($column)) {
            $rule .= ",$column";
        }

        if ($args) {
            // Add optional arguments
            foreach ($args as $arg) {
                $rule .= ",$arg";
            }
        }

        $this->addRule("exists:$rule");
        return $this;
    }