发送邮件的时候，接口会卡住半天，需要异步执行代码，

即：接口数据直接返回，而邮件通知在后台运行

1、使用curl实现


$start_time = time();

$url = 'https://www.google.com/';

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_TIMEOUT, 1);
curl_exec($ch);
curl_close($ch);

$end_time = time();

echo 'done: ' . ($end_time - $start_time);

2、使用 Requests 实现

Requests 基于curl，所以和方式1是一样的

composer require rmccue/requests

<?php

require './vendor/autoload.php';


$start_time = time();

$url = 'https://www.google.com/';

try {
    $res = Requests::get($url, [], ['timeout' => 1]);
} catch (Exception $e) {
    echo 'Exception' . PHP_EOL;
}

$end_time = time();
echo 'done: ' . ($end_time - $start_time);

以上两种方式都可以实现异步调用，缺点是必须有1秒的延时…

3、使用 register_shutdown_function 实现

<?php

class AsyncHook
{

    private static $hook_list = array();
    private static $hooked = false;

    /**
     * hook函数fastcgi_finish_request执行
     *
     * @param callback $callback
     * @param array $params
     */
    public static function hook($callback, $params = [])
    {
        self::$hook_list[] = array('callback' => $callback, 'params' => $params);

        if (self::$hooked == false) {
            self::$hooked = true;
            register_shutdown_function(array(__CLASS__, '__run'));
        }
    }

    /**
     * 由系统调用
     *
     * @return void
     */
    public static function __run()
    {
        if (function_exists('fastcgi_finish_request')) {
            fastcgi_finish_request();
        }

        if (empty(self::$hook_list)) {
            return;
        }

        foreach (self::$hook_list as $hook) {
            $callback = $hook['callback'];
            $params   = $hook['params'];
            call_user_func_array($callback, $params);
        }
    }
}

测试

function timer()
{
    sleep(5);
    echo 'timer done';
}


$start_time = time();

AsyncHook::hook('timer');

$end_time = time();

echo 'done: ' . ($end_time - $start_time) . PHP_EOL;
// done: 0
// timer done

该方法会继续执行代码，执行完成后并不会直接退出，而是会等待调用的方式都执行结束

参考
PHP实现异步调用方法研究
PHP 异步执行方式