async_request.php

<?php

function async_request($method, $url, $params, array $headers = [])
{

    $method = strtoupper($method);

    $data = http_build_query($params);

    $parts = parse_url($url) + [
        'port'  => 80,
        'path'  => '/',
    ];

    $headers += [
        'Content-Type'   => 'application/x-www-form-urlencoded',
        'Host'           => $parts['host'],
        'Content-Length' => $method == 'GET' ? 0 : strlen($data),
        'Connection'     => 'Close',
    ];

    $path = ($method == 'GET') ? $parts['path'] . '?' . $data : $parts['path'];

    $output_header = sprintf('%s %s HTTP/1.1', $method, $path) . "\r\n";

    foreach ($headers as $name => $value)
    {
        foreach((array) $value as $v)
        {
            $output_header .= "$name: $v\r\n";
        }
    }

    $output_header .= "\r\n";

    $handle = @fsockopen($parts['host'], $parts['port'], $_errno, $_errstr, 30);

    if ($handle === false)
    {
        throw new \RuntimeException($_errstr);
    }

    fwrite($handle, $output_header);

    if ($method !== 'GET') fwrite($handle, $data);

    fclose($handle);

    return $output_header;

}