cURL asynchronous requests using curl_multi and callbacks

example.php

<?php

require('Requests.php');

// We want the requests to be mixed fast/slow so we can see if it's working

$slow = 'http://localhost/curl_multi/slow.php';
$fast = 'http://localhost/curl_multi/fast.php';

$urls = array();
for ($i = 0; $i < 10; $i++)
{
	if($i % 2)
	{
		print "Slow\n";
		$urls[] = $slow;
	}
	else
	{
		print "Fast\n";
		$urls[] = $fast;
	}
}


$callback = function($data, $info)
{
	print "Callback: ";
	print_r($data);
	print_r($info);
};


$requests = new Requests();
$requests->process($urls, $callback);

fast.php

<?php

usleep(mt_rand(10000, 200000));
print basename(__FILE__) . "\n";

Requests.php

<?php
/**
 * Make asynchronous requests to different resources as fast as possible and process the results as they are ready.
 */
class Requests
{
	public $handle;

	public function __construct()
	{
		$this->handle = curl_multi_init();
	}

	public function process($urls, $callback)
	{
		foreach($urls as $url)
		{
			$ch = curl_init($url);
			curl_setopt_array($ch, array(CURLOPT_RETURNTRANSFER => TRUE));
			curl_multi_add_handle($this->handle, $ch);
		}

		do {
			$mrc = curl_multi_exec($this->handle, $active);

			if ($state = curl_multi_info_read($this->handle))
			{
				//print_r($state);
				$info = curl_getinfo($state['handle']);
				//print_r($info);
				$callback(curl_multi_getcontent($state['handle']), $info);
				curl_multi_remove_handle($this->handle, $state['handle']);
			}

			usleep(10000); // stop wasting CPU cycles and rest for a couple ms

		} while ($mrc == CURLM_CALL_MULTI_PERFORM || $active);

	}

	public function __destruct()
	{
		curl_multi_close($this->handle);
	}
}

rolling_curl.php

<?php
// This limits the request rate to the size of the $rolling_window
// http://www.onlineaspect.com/2009/01/26/how-to-use-curl_multi-without-blocking/
function rolling_curl($urls, $callback, $custom_options = null)
{

	// make sure the rolling window isn't greater than the # of urls
	$rolling_window = 5;
	$rolling_window = (sizeof($urls) < $rolling_window) ? sizeof($urls) : $rolling_window;

	$master = curl_multi_init();
	$curl_arr = array();

	// add additional curl options here
	$std_options = array(
		CURLOPT_RETURNTRANSFER => true,
		CURLOPT_FOLLOWLOCATION => true,
		CURLOPT_MAXREDIRS => 5
	);

	$options = ($custom_options) ? ($std_options + $custom_options) : $std_options;

	// start the first batch of requests
	for ($i = 0; $i < $rolling_window; $i++)
	{
		$ch = curl_init();
		$options[CURLOPT_URL] = $urls[$i];
		curl_setopt_array($ch,$options);
		curl_multi_add_handle($master, $ch);
	}

	do {
		while(($execrun = curl_multi_exec($master, $running)) == CURLM_CALL_MULTI_PERFORM);
			if($execrun != CURLM_OK)
				break;

		// a request was just completed -- find out which one
		while($done = curl_multi_info_read($master))
		{
			$info = curl_getinfo($done['handle']);

			$output = curl_multi_getcontent($done['handle']);

			// request successful.  process output using the callback function.
			$callback($output, $info);

			if(isset($urls[$i + 1]))
			{
				// start a new request (it's important to do this before removing the old one)
				$ch = curl_init();
				$options[CURLOPT_URL] = $urls[$i++];  // increment i
				curl_setopt_array($ch,$options);
				curl_multi_add_handle($master, $ch);
			}

			// remove the curl handle that just completed
			curl_multi_remove_handle($master, $done['handle']);
		}

		usleep(10000); // stop wasting CPU cycles and rest for a couple ms

	} while ($running);

	curl_multi_close($master);
}

slow.php

<?php

usleep(mt_rand(100000, 600000));
print basename(__FILE__) . "\n";

Hi Thanks for your code. I am pretty newbie in php, and have 2 questions:

1. How can I pass POST data in the request?
2. After I change your slow.php file's sleeping time, say change it to a constant value, then for the slow.php I can only get 1 print within the callback, which seems to me the callback is called only ONCE. However, if it is really asynchronous call, the response should be uniquely identified by some id right? and all 5 slow.php should call the callback once, is it a bug?
   Thanks again for your time,
   very appreciated.

This is still blocking, just not blocking in the curl call (but in your loop instead).

@abiusx have you yet learned that all async await eventually blocks? This is just kinda low-level way to get async / await prior to those features in PHP.

https://github.com/guzzle/guzzle/search?q=CurlMultiHandler