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));

您可以使用exec()来调用一些可以执行HTTP请求的东西，如wget，但必须将程序的所有输出指向某个地方，如文件或/dev/null，否则PHP进程将等待该输出。

如果你想把进程和apache线程完全分开，可以尝试这样做(我不确定，但我希望你能明白):

exec('bash -c "wget -O (url goes here) > /dev/null 2>&1 &"');

这不是一项很好的业务，您可能需要类似cron作业的东西来调用heartbeat脚本，该脚本轮询实际的数据库事件队列来执行真正的异步事件。

Symfony HttpClient是异步的https://symfony.com/doc/current/components/http_client.html。

例如，你可以

use Symfony\Component\HttpClient\HttpClient;

$client = HttpClient::create();
$response1 = $client->request('GET', 'https://website1');
$response2 = $client->request('GET', 'https://website1');
$response3 = $client->request('GET', 'https://website1');
//these 3 calls with return immediately
//but the requests will fire to the website1 webserver

$response1->getContent(); //this will block until content is fetched
$response2->getContent(); //same 
$response3->getContent(); //same

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。

这是我自己的PHP函数，当我做POST到任何页面的特定URL .... 示例:my Function的***用法…

    <?php
        parse_str("email=myemail@ehehehahaha.com&subject=this is just a test");
        $_POST['email']=$email;
        $_POST['subject']=$subject;
        echo HTTP_POST("http://example.com/mail.php",$_POST);***

    exit;
    ?>
    <?php
    /*********HTTP POST using FSOCKOPEN **************/
    // by ArbZ

function HTTP_Post($URL,$data, $referrer="") {

    // parsing the given URL
    $URL_Info=parse_url($URL);

    // Building referrer
    if($referrer=="") // if not given use this script as referrer
        $referrer=$_SERVER["SCRIPT_URI"];

    // making string from $data
    foreach($data as $key=>$value)
        $values[]="$key=".urlencode($value);
        $data_string=implode("&",$values);

    // Find out which port is needed - if not given use standard (=80)
    if(!isset($URL_Info["port"]))
        $URL_Info["port"]=80;

    // building POST-request: HTTP_HEADERs
    $request.="POST ".$URL_Info["path"]." HTTP/1.1\n";
    $request.="Host: ".$URL_Info["host"]."\n";
    $request.="Referer: $referer\n";
    $request.="Content-type: application/x-www-form-urlencoded\n";
    $request.="Content-length: ".strlen($data_string)."\n";
    $request.="Connection: close\n";
    $request.="\n";
    $request.=$data_string."\n";

    $fp = fsockopen($URL_Info["host"],$URL_Info["port"]);
    fputs($fp, $request);
    while(!feof($fp)) {
        $result .= fgets($fp, 128);
    }
    fclose($fp); //$eco = nl2br();


    function getTextBetweenTags($string, $tagname) {
        $pattern = "/<$tagname ?.*>(.*)<\/$tagname>/";
        preg_match($pattern, $string, $matches);
        return $matches[1];
    }
    //STORE THE FETCHED CONTENTS to a VARIABLE, because its way better and fast...
    $str = $result;
    $txt = getTextBetweenTags($str, "span"); $eco = $txt;  $result = explode("&",$result);
    return $result[1];
    <span style=background-color:LightYellow;color:blue>".trim($_GET['em'])."</span>
    </pre> "; 
}
</pre>

/**
 * Asynchronously execute/include a PHP file. Does not record the output of the file anywhere. 
 *
 * @param string $filename              file to execute, relative to calling script
 * @param string $options               (optional) arguments to pass to file via the command line
 */ 
function asyncInclude($filename, $options = '') {
    exec("/path/to/php -f {$filename} {$options} >> /dev/null &");
}