This example will create curl handles for a list of URLs, add them to a multi handle, and process them asynchronously.

<?php

$urls = [
    "https://www.php.net/",
    "https://www.example.com/",
];

$mh = curl_multi_init();
$map = new WeakMap();

foreach ($urls as $url) {
    $ch = curl_init($url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    curl_multi_add_handle($mh, $ch);
    $map[$ch] = $url;
}

do {
    $status = curl_multi_exec($mh, $unfinishedHandles);
    if ($status !== CURLM_OK) {
        throw new \Exception(curl_multi_strerror(curl_multi_errno($mh)));
    }

    while (($info = curl_multi_info_read($mh)) !== false) {
        if ($info['msg'] === CURLMSG_DONE) {
            $handle = $info['handle'];
            curl_multi_remove_handle($mh, $handle);
            $url = $map[$handle];

            if ($info['result'] === CURLE_OK) {
                $statusCode = curl_getinfo($handle, CURLINFO_HTTP_CODE);

                echo "Request to {$url} finished with HTTP status {$statusCode}:", PHP_EOL;
                echo curl_multi_getcontent($handle);
                echo PHP_EOL, PHP_EOL;
            } else {
                echo "Request to {$url} failed with error: ", PHP_EOL;
                echo curl_strerror($info['result']);
                echo PHP_EOL, PHP_EOL;
            }
        }
    }

    if ($unfinishedHandles) {
        if (($updatedHandles = curl_multi_select($mh)) === -1) {
            throw new \Exception(curl_multi_strerror(curl_multi_errno($mh)));
        }
    }
} while ($unfinishedHandles);

curl_multi_close($mh);

?>