您可以使用这个库:https://github.com/stil/curl-easy

这很简单:

<?php
$request = new cURL\Request('http://yahoo.com/');
$request->getOptions()->set(CURLOPT_RETURNTRANSFER, true);

// Specify function to be called when your request is complete
$request->addListener('complete', function (cURL\Event $event) {
    $response = $event->response;
    $httpCode = $response->getInfo(CURLINFO_HTTP_CODE);
    $html = $response->getContent();
    echo "\nDone.\n";
});

// Loop below will run as long as request is processed
$timeStart = microtime(true);
while ($request->socketPerform()) {
    printf("Running time: %dms    \r", (microtime(true) - $timeStart)*1000);
    // Here you can do anything else, while your request is in progress
}

下面你可以看到上面例子的控制台输出。 它将显示简单的实时时钟，指示请求正在运行的时间:

如果你控制了你想要异步调用的目标(例如你自己的"longtask.php")，你可以从那端关闭连接，两个脚本将并行运行。它是这样工作的:

quick.php通过cURL打开longtask.php(这里没有魔法) php关闭连接并继续(神奇!) 当连接关闭时，cURL返回quick.php 两项任务同时进行

我试过了，效果不错。但是quick.php不会知道longtask.php正在做什么，除非您在进程之间创建一些通信方式。

在执行其他操作之前，请先在longtask.php中尝试这段代码。它将关闭连接，但仍然继续运行(并抑制任何输出):

while(ob_get_level()) ob_end_clean();
header('Connection: close');
ignore_user_abort();
ob_start();
echo('Connection Closed');
$size = ob_get_length();
header("Content-Length: $size");
ob_end_flush();
flush();

代码复制自PHP手册的用户贡献注释，并进行了一些改进。

下面是一个工作示例，只需运行它，然后打开storage.txt，检查神奇的结果

<?php
    function curlGet($target){
        $ch = curl_init();
        curl_setopt($ch, CURLOPT_URL, $target);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
        $result = curl_exec ($ch);
        curl_close ($ch);
        return $result;
    }

    // Its the next 3 lines that do the magic
    ignore_user_abort(true);
    header("Connection: close"); header("Content-Length: 0");
    echo str_repeat("s", 100000); flush();

    $i = $_GET['i'];
    if(!is_numeric($i)) $i = 1;
    if($i > 4) exit;
    if($i == 1) file_put_contents('storage.txt', '');

    file_put_contents('storage.txt', file_get_contents('storage.txt') . time() . "\n");

    sleep(5);
    curlGet($_SERVER['HTTP_HOST'] . $_SERVER['SCRIPT_NAME'] . '?i=' . ($i + 1));
    curlGet($_SERVER['HTTP_HOST'] . $_SERVER['SCRIPT_NAME'] . '?i=' . ($i + 1));

ReactPHP异步http客户端 https://github.com/shuchkin/react-http-client

通过Composer安装

$ composer require shuchkin/react-http-client

异步HTTP GET

// get.php
$loop = \React\EventLoop\Factory::create();

$http = new \Shuchkin\ReactHTTP\Client( $loop );

$http->get( 'https://tools.ietf.org/rfc/rfc2068.txt' )->then(
    function( $content ) {
        echo $content;
    },
    function ( \Exception $ex ) {
        echo 'HTTP error '.$ex->getCode().' '.$ex->getMessage();
    }
);

$loop->run();

在cli模式下运行php

$ php get.php

class async_file_get_contents extends Thread{
    public $ret;
    public $url;
    public $finished;
        public function __construct($url) {
        $this->finished=false;
        $this->url=$url;
    }
        public function run() {
        $this->ret=file_get_contents($this->url);
        $this->finished=true;
    }
}
$afgc=new async_file_get_contents("http://example.org/file.ext");

我之前接受的答案行不通。它仍在等待回应。这虽然工作，采取从我如何使一个异步GET请求在PHP?

function post_without_wait($url, $params)
{
    foreach ($params as $key => &$val) {
      if (is_array($val)) $val = implode(',', $val);
        $post_params[] = $key.'='.urlencode($val);
    }
    $post_string = implode('&', $post_params);

    $parts=parse_url($url);

    $fp = fsockopen($parts['host'],
        isset($parts['port'])?$parts['port']:80,
        $errno, $errstr, 30);

    $out = "POST ".$parts['path']." HTTP/1.1\r\n";
    $out.= "Host: ".$parts['host']."\r\n";
    $out.= "Content-Type: application/x-www-form-urlencoded\r\n";
    $out.= "Content-Length: ".strlen($post_string)."\r\n";
    $out.= "Connection: Close\r\n\r\n";
    if (isset($post_string)) $out.= $post_string;

    fwrite($fp, $out);
    fclose($fp);
}