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

超时可以设置为毫秒， 参见http://www.php.net/manual/en/function.curl-setopt中的“CURLOPT_CONNECTTIMEOUT_MS”

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);

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));

使用CURL设置低CURLOPT_TIMEOUT_MS来模拟请求中止 设置ignore_user_abort(true)在连接关闭后继续处理。

使用这种方法，不需要通过头文件和缓冲区来实现连接处理，这太依赖于操作系统，浏览器和PHP版本

主进程

function async_curl($background_process=''){

    //-------------get curl contents----------------

    $ch = curl_init($background_process);
    curl_setopt_array($ch, array(
        CURLOPT_HEADER => 0,
        CURLOPT_RETURNTRANSFER =>true,
        CURLOPT_NOSIGNAL => 1, //to timeout immediately if the value is < 1000 ms
        CURLOPT_TIMEOUT_MS => 50, //The maximum number of mseconds to allow cURL functions to execute
        CURLOPT_VERBOSE => 1,
        CURLOPT_HEADER => 1
    ));
    $out = curl_exec($ch);

    //-------------parse curl contents----------------

    //$header_size = curl_getinfo($ch, CURLINFO_HEADER_SIZE);
    //$header = substr($out, 0, $header_size);
    //$body = substr($out, $header_size);

    curl_close($ch);

    return true;
}

async_curl('http://example.com/background_process_1.php');

后台进程

ignore_user_abort(true);

//do something...

NB

如果希望cURL在不到一秒的时间内超时，可以使用 CURLOPT_TIMEOUT_MS，尽管在类unix上有一个bug/“特性” 如果值为<，则会导致libcurl立即超时。 1000毫秒，错误“cURL错误(28):超时已达”。的 这种行为的解释是: […] 解决方案是使用CURLOPT_NOSIGNAL禁用信号

资源

卷曲超时小于1000毫秒总是失败? http://www.php.net/manual/en/function.curl-setopt.php#104597 http://php.net/manual/en/features.connection-handling.php