How to Make an Asynchronous Get Request in PHP

How to make asynchronous HTTP requests in PHP

The answer I'd previously accepted didn't work. It still waited for responses. This does work though, taken from How do I make an asynchronous GET request in 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);
}

How do I make an asynchronous GET request in PHP?

file_get_contents will do what you want

$output = file_get_contents('http://www.example.com/');
echo $output;

Edit: One way to fire off a GET request and return immediately.

Quoted from http://petewarden.typepad.com/searchbrowser/2008/06/how-to-post-an.html

function curl_post_async($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);
}

What this does is open a socket, fire off a get request, and immediately close the socket and return.

PHP Asynchronous HTTP request with response

file_get_contents is a synchronous function, so when you call it 10 times, you call it 10 times sequentially. You need to make requests in parallel. curl_multi_* methods family is probably what you are looking for. If you are not familiar with curl enough it may be tricky to implement it correctly, so I'd recommend you to use some library for that.

You can take a look at this library https://github.com/petewarden/ParallelCurl

Async get request

I found this website that details curl_multi_* functions, which worked for me.

Asynchronous HTTP requests in PHP

Yes, depending on the traffic of your site, spawning a separate PHP process for running a script could be devastating. It would be more efficient to use shell_exec() to start a background process that saves the output to a filename you already know, but even this could be resource intensive.

You could also have a request queue stored in a database. A single, separate background process would pull the job, execute it, and save the output, possibly setting a flag in the DB that your web process could check.

If you're going to use the DB queue approach, use curl_multi* class of functions to send all queued requests at once. This will limit the execution time of each iteration in your background process to the longest request time.

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