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:

swoole扩展。https://github.com/matyhtf/swoole PHP的异步并发网络框架。

$client = new swoole_client(SWOOLE_SOCK_TCP, SWOOLE_SOCK_ASYNC);

$client->on("connect", function($cli) {
    $cli->send("hello world\n");
});

$client->on("receive", function($cli, $data){
    echo "Receive: $data\n";
});

$client->on("error", function($cli){
    echo "connect fail\n";
});

$client->on("close", function($cli){
    echo "close\n";
});

$client->connect('127.0.0.1', 9501, 0.5);

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

截至2018年，Guzzle已经成为HTTP请求事实上的标准库，在几个现代框架中使用。它是用纯PHP编写的，不需要安装任何自定义扩展。

它可以很好地执行异步HTTP调用，甚至可以在需要执行100个HTTP调用，但不想一次运行超过5个的情况下将它们合并在一起。

并发请求示例

use GuzzleHttp\Client;
use GuzzleHttp\Promise;

$client = new Client(['base_uri' => 'http://httpbin.org/']);

// Initiate each request but do not block
$promises = [
    'image' => $client->getAsync('/image'),
    'png'   => $client->getAsync('/image/png'),
    'jpeg'  => $client->getAsync('/image/jpeg'),
    'webp'  => $client->getAsync('/image/webp')
];

// Wait on all of the requests to complete. Throws a ConnectException
// if any of the requests fail
$results = Promise\unwrap($promises);

// Wait for the requests to complete, even if some of them fail
$results = Promise\settle($promises)->wait();

// You can access each result using the key provided to the unwrap
// function.
echo $results['image']['value']->getHeader('Content-Length')[0]
echo $results['png']['value']->getHeader('Content-Length')[0]

看到http://docs.guzzlephp.org/en/stable/quickstart.html并发请求

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));

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);
}