php 异步请求

        $ch = curl_init();
        $curl_opt = array(
            CURLOPT_URL            => $url,
            CURLOPT_RETURNTRANSFER => 1,
            CURLOPT_TIMEOUT        => 1
        );
        curl_setopt_array($ch, $curl_opt);
        curl_exec($ch);
        curl_close($ch);