[php] How to make asynchronous HTTP requests in PHP

Is there a way in PHP to make asynchronous HTTP calls? I don't care about the response, I just want to do something like file_get_contents(), but not wait for the request to finish before executing the rest of my code. This would be super useful for setting off "events" of a sort in my application, or triggering long processes.

Any ideas?

Well, the timeout can be set in milliseconds, see "CURLOPT_CONNECTTIMEOUT_MS" in http://www.php.net/manual/en/function.curl-setopt

You can use this library: https://github.com/stil/curl-easy

It's pretty straightforward then:

<?php
$request = new cURL\Request('http://yahoo.com/');
$request->getOptions()->set(CURLOPT_RETURNTRANSFER, true);

// Specify function to be called when your request is complete
$request->addListener('complete', function (cURL\Event $event) {
    $response = $event->response;
    $httpCode = $response->getInfo(CURLINFO_HTTP_CODE);
    $html = $response->getContent();
    echo "\nDone.\n";
});

// Loop below will run as long as request is processed
$timeStart = microtime(true);
while ($request->socketPerform()) {
    printf("Running time: %dms    \r", (microtime(true) - $timeStart)*1000);
    // Here you can do anything else, while your request is in progress
}

Below you can see console output of above example. It will display simple live clock indicating how much time request is running:

Symfony HttpClient is asynchronous https://symfony.com/doc/current/components/http_client.html.

For example you can

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

1. Fake a request abortion using CURL setting a low CURLOPT_TIMEOUT_MS

2. set ignore_user_abort(true) to keep processing after the connection closed.

With this method no need to implement connection handling via headers and buffer too dependent on OS, Browser and PHP version

Master process

function async_curl($background_process=''){

    //-------------get curl contents----------------

    $ch = curl_init($background_process);
    curl_setopt_array($ch, array(
        CURLOPT_HEADER => 0,
        CURLOPT_RETURNTRANSFER =>true,
        CURLOPT_NOSIGNAL => 1, //to timeout immediately if the value is < 1000 ms
        CURLOPT_TIMEOUT_MS => 50, //The maximum number of mseconds to allow cURL functions to execute
        CURLOPT_VERBOSE => 1,
        CURLOPT_HEADER => 1
    ));
    $out = curl_exec($ch);

    //-------------parse curl contents----------------

    //$header_size = curl_getinfo($ch, CURLINFO_HEADER_SIZE);
    //$header = substr($out, 0, $header_size);
    //$body = substr($out, $header_size);

    curl_close($ch);

    return true;
}

async_curl('http://example.com/background_process_1.php');

Background process

ignore_user_abort(true);

//do something...

NB

If you want cURL to timeout in less than one second, you can use CURLOPT_TIMEOUT_MS, although there is a bug/"feature" on "Unix-like systems" that causes libcurl to timeout immediately if the value is < 1000 ms with the error "cURL Error (28): Timeout was reached". The explanation for this behavior is:

[...]

The solution is to disable signals using CURLOPT_NOSIGNAL

Resources

• curl timeout less than 1000ms always fails?

• http://www.php.net/manual/en/function.curl-setopt.php#104597

• http://php.net/manual/en/features.connection-handling.php

Here is my own PHP function when I do POST to a specific URL of any page.... Sample: *** usage of my Function...

    <?php
        parse_str("[email protected]&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 &");
}

If you control the target that you want to call asynchronously (e.g. your own "longtask.php"), you can close the connection from that end, and both scripts will run in parallel. It works like this:

1. quick.php opens longtask.php via cURL (no magic here)
2. longtask.php closes the connection and continues (magic!)
3. cURL returns to quick.php when the connection is closed
4. Both tasks continue in parallel

I have tried this, and it works just fine. But quick.php won't know anything about how longtask.php is doing, unless you create some means of communication between the processes.

Try this code in longtask.php, before you do anything else. It will close the connection, but still continue to run (and suppress any output):

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();

The code is copied from the PHP manual's user contributed notes and somewhat improved.

let me show you my way :)

needs nodejs installed on the server

(my server sends 1000 https get request takes only 2 seconds)

url.php :

<?
$urls = array_fill(0, 100, 'http://google.com/blank.html');

function execinbackground($cmd) { 
    if (substr(php_uname(), 0, 7) == "Windows"){ 
        pclose(popen("start /B ". $cmd, "r"));  
    } 
    else { 
        exec($cmd . " > /dev/null &");   
    } 
} 
fwite(fopen("urls.txt","w"),implode("\n",$urls);
execinbackground("nodejs urlscript.js urls.txt");
// { do your work while get requests being executed.. }
?>

urlscript.js >

var https = require('https');
var url = require('url');
var http = require('http');
var fs = require('fs');
var dosya = process.argv[2];
var logdosya = 'log.txt';
var count=0;
http.globalAgent.maxSockets = 300;
https.globalAgent.maxSockets = 300;

setTimeout(timeout,100000); // maximum execution time (in ms)

function trim(string) {
    return string.replace(/^\s*|\s*$/g, '')
}

fs.readFile(process.argv[2], 'utf8', function (err, data) {
    if (err) {
        throw err;
    }
    parcala(data);
});

function parcala(data) {
    var data = data.split("\n");
    count=''+data.length+'-'+data[1];
    data.forEach(function (d) {
        req(trim(d));
    });
    /*
    fs.unlink(dosya, function d() {
        console.log('<%s> file deleted', dosya);
    });
    */
}


function req(link) {
    var linkinfo = url.parse(link);
    if (linkinfo.protocol == 'https:') {
        var options = {
        host: linkinfo.host,
        port: 443,
        path: linkinfo.path,
        method: 'GET'
    };
https.get(options, function(res) {res.on('data', function(d) {});}).on('error', function(e) {console.error(e);});
    } else {
    var options = {
        host: linkinfo.host,
        port: 80,
        path: linkinfo.path,
        method: 'GET'
    };        
http.get(options, function(res) {res.on('data', function(d) {});}).on('error', function(e) {console.error(e);});
    }
}


process.on('exit', onExit);

function onExit() {
    log();
}

function timeout()
{
console.log("i am too far gone");process.exit();
}

function log() 
{
    var fd = fs.openSync(logdosya, 'a+');
    fs.writeSync(fd, dosya + '-'+count+'\n');
    fs.closeSync(fd);
}

You can use non-blocking sockets and one of pecl extensions for PHP:

• http://php.net/event
• http://php.net/libevent
• http://php.net/ev
• https://github.com/m4rw3r/php-libev

You can use library which gives you an abstraction layer between your code and a pecl extension: https://github.com/reactphp/event-loop

You can also use async http-client, based on the previous library: https://github.com/reactphp/http-client

See others libraries of ReactPHP: http://reactphp.org

Be careful with an asynchronous model. I recommend to see this video on youtube: http://www.youtube.com/watch?v=MWNcItWuKpI

You can do trickery by using exec() to invoke something that can do HTTP requests, like wget, but you must direct all output from the program to somewhere, like a file or /dev/null, otherwise the PHP process will wait for that output.

If you want to separate the process from the apache thread entirely, try something like (I'm not sure about this, but I hope you get the idea):

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

It's not a nice business, and you'll probably want something like a cron job invoking a heartbeat script which polls an actual database event queue to do real asynchronous events.

I find this package quite useful and very simple: https://github.com/amphp/parallel-functions

<?php

use function Amp\ParallelFunctions\parallelMap;
use function Amp\Promise\wait;

$responses = wait(parallelMap([
    'https://google.com/',
    'https://github.com/',
    'https://stackoverflow.com/',
], function ($url) {
    return file_get_contents($url);
}));

It will load all 3 urls in parallel. You can also use class instance methods in the closure.

For example I use Laravel extension based on this package https://github.com/spatie/laravel-collection-macros#parallelmap

Here is my code:

    /**
     * Get domains with all needed data
     */
    protected function getDomainsWithdata(): Collection
    {
        return $this->opensrs->getDomains()->parallelMap(function ($domain) {
            $contact = $this->opensrs->getDomainContact($domain);
            $contact['domain'] = $domain;
            return $contact;
        }, 10);
    }

It loads all needed data in 10 parallel threads and instead of 50 secs without async it finished in just 8 secs.

As of 2018, Guzzle has become the defacto standard library for HTTP requests, used in several modern frameworks. It's written in pure PHP and does not require installing any custom extensions.

It can do asynchronous HTTP calls very nicely, and even pool them such as when you need to make 100 HTTP calls, but don't want to run more than 5 at a time.

Concurrent request example

use GuzzleHttp\Client;
use GuzzleHttp\Promise;

$client = new Client(['base_uri' => 'http://httpbin.org/']);

// Initiate each request but do not block
$promises = [
    'image' => $client->getAsync('/image'),
    'png'   => $client->getAsync('/image/png'),
    'jpeg'  => $client->getAsync('/image/jpeg'),
    'webp'  => $client->getAsync('/image/webp')
];

// Wait on all of the requests to complete. Throws a ConnectException
// if any of the requests fail
$results = Promise\unwrap($promises);

// Wait for the requests to complete, even if some of them fail
$results = Promise\settle($promises)->wait();

// You can access each result using the key provided to the unwrap
// function.
echo $results['image']['value']->getHeader('Content-Length')[0]
echo $results['png']['value']->getHeader('Content-Length')[0]

See http://docs.guzzlephp.org/en/stable/quickstart.html#concurrent-requests

class async_file_get_contents extends Thread{
    public $ret;
    public $url;
    public $finished;
        public function __construct($url) {
        $this->finished=false;
        $this->url=$url;
    }
        public function run() {
        $this->ret=file_get_contents($this->url);
        $this->finished=true;
    }
}
$afgc=new async_file_get_contents("http://example.org/file.ext");

The swoole extension. https://github.com/matyhtf/swoole Asynchronous & concurrent networking framework for PHP.

$client = new swoole_client(SWOOLE_SOCK_TCP, SWOOLE_SOCK_ASYNC);

$client->on("connect", function($cli) {
    $cli->send("hello world\n");
});

$client->on("receive", function($cli, $data){
    echo "Receive: $data\n";
});

$client->on("error", function($cli){
    echo "connect fail\n";
});

$client->on("close", function($cli){
    echo "close\n";
});

$client->connect('127.0.0.1', 9501, 0.5);

Here is a working example, just run it and open storage.txt afterwards, to check the magical result

<?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));

Event Extension

Event extension is very appropriate. It is a port of Libevent library which is designed for event-driven I/O, mainly for networking.

I have written a sample HTTP client that allows to schedule a number of HTTP requests and run them asynchronously.

This is a sample HTTP client class based on Event extension.

The class allows to schedule a number of HTTP requests, then run them asynchronously.

http-client.php

<?php
class MyHttpClient {
  /// @var EventBase
  protected $base;
  /// @var array Instances of EventHttpConnection
  protected $connections = [];

  public function __construct() {
    $this->base = new EventBase();
  }

  /**
   * Dispatches all pending requests (events)
   *
   * @return void
   */
  public function run() {
    $this->base->dispatch();
  }

  public function __destruct() {
    // Destroy connection objects explicitly, don't wait for GC.
    // Otherwise, EventBase may be free'd earlier.
    $this->connections = null;
  }

  /**
   * @brief Adds a pending HTTP request
   *
   * @param string $address Hostname, or IP
   * @param int $port Port number
   * @param array $headers Extra HTTP headers
   * @param int $cmd A EventHttpRequest::CMD_* constant
   * @param string $resource HTTP request resource, e.g. '/page?a=b&c=d'
   *
   * @return EventHttpRequest|false
   */
  public function addRequest($address, $port, array $headers,
    $cmd = EventHttpRequest::CMD_GET, $resource = '/')
  {
    $conn = new EventHttpConnection($this->base, null, $address, $port);
    $conn->setTimeout(5);

    $req = new EventHttpRequest([$this, '_requestHandler'], $this->base);

    foreach ($headers as $k => $v) {
      $req->addHeader($k, $v, EventHttpRequest::OUTPUT_HEADER);
    }
    $req->addHeader('Host', $address, EventHttpRequest::OUTPUT_HEADER);
    $req->addHeader('Connection', 'close', EventHttpRequest::OUTPUT_HEADER);
    if ($conn->makeRequest($req, $cmd, $resource)) {
      $this->connections []= $conn;
      return $req;
    }

    return false;
  }


  /**
   * @brief Handles an HTTP request
   *
   * @param EventHttpRequest $req
   * @param mixed $unused
   *
   * @return void
   */
  public function _requestHandler($req, $unused) {
    if (is_null($req)) {
      echo "Timed out\n";
    } else {
      $response_code = $req->getResponseCode();

      if ($response_code == 0) {
        echo "Connection refused\n";
      } elseif ($response_code != 200) {
        echo "Unexpected response: $response_code\n";
      } else {
        echo "Success: $response_code\n";
        $buf = $req->getInputBuffer();
        echo "Body:\n";
        while ($s = $buf->readLine(EventBuffer::EOL_ANY)) {
          echo $s, PHP_EOL;
        }
      }
    }
  }
}


$address = "my-host.local";
$port = 80;
$headers = [ 'User-Agent' => 'My-User-Agent/1.0', ];

$client = new MyHttpClient();

// Add pending requests
for ($i = 0; $i < 10; $i++) {
  $client->addRequest($address, $port, $headers,
    EventHttpRequest::CMD_GET, '/test.php?a=' . $i);
}

// Dispatch pending requests
$client->run();

test.php

This is a sample script on the server side.

<?php
echo 'GET: ', var_export($_GET, true), PHP_EOL;
echo 'User-Agent: ', $_SERVER['HTTP_USER_AGENT'] ?? '(none)', PHP_EOL;

Usage

php http-client.php

Sample Output

Success: 200
Body:
GET: array (
  'a' => '1',
)
User-Agent: My-User-Agent/1.0
Success: 200
Body:
GET: array (
  'a' => '0',
)
User-Agent: My-User-Agent/1.0
Success: 200
Body:
GET: array (
  'a' => '3',
)
...

(Trimmed.)

Note, the code is designed for long-term processing in the CLI SAPI.

For custom protocols, consider using low-level API, i.e. buffer events, buffers. For SSL/TLS communications, I would recommend the low-level API in conjunction with Event's ssl context. Examples:

• SSL echo server
• SSL client

Although Libevent's HTTP API is simple, it is not as flexible as buffer events. For example, the HTTP API currently doesn't support custom HTTP methods. But it is possible to implement virtually any protocol using the low-level API.

Ev Extension

I have also written a sample of another HTTP client using Ev extension with sockets in non-blocking mode. The code is slightly more verbose than the sample based on Event, because Ev is a general purpose event loop. It doesn't provide network-specific functions, but its EvIo watcher is capable of listening to a file descriptor encapsulated into the socket resource, in particular.

This is a sample HTTP client based on Ev extension.

Ev extension implements a simple yet powerful general purpose event loop. It doesn't provide network-specific watchers, but its I/O watcher can be used for asynchronous processing of sockets.

The following code shows how HTTP requests can be scheduled for parallel processing.

http-client.php

<?php
class MyHttpRequest {
  /// @var MyHttpClient
  private $http_client;
  /// @var string
  private $address;
  /// @var string HTTP resource such as /page?get=param
  private $resource;
  /// @var string HTTP method such as GET, POST etc.
  private $method;
  /// @var int
  private $service_port;
  /// @var resource Socket
  private $socket;
  /// @var double Connection timeout in seconds.
  private $timeout = 10.;
  /// @var int Chunk size in bytes for socket_recv()
  private $chunk_size = 20;
  /// @var EvTimer
  private $timeout_watcher;
  /// @var EvIo
  private $write_watcher;
  /// @var EvIo
  private $read_watcher;
  /// @var EvTimer
  private $conn_watcher;
  /// @var string buffer for incoming data
  private $buffer;
  /// @var array errors reported by sockets extension in non-blocking mode.
  private static $e_nonblocking = [
    11, // EAGAIN or EWOULDBLOCK
    115, // EINPROGRESS
  ];

  /**
   * @param MyHttpClient $client
   * @param string $host Hostname, e.g. google.co.uk
   * @param string $resource HTTP resource, e.g. /page?a=b&c=d
   * @param string $method HTTP method: GET, HEAD, POST, PUT etc.
   * @throws RuntimeException
   */
  public function __construct(MyHttpClient $client, $host, $resource, $method) {
    $this->http_client = $client;
    $this->host        = $host;
    $this->resource    = $resource;
    $this->method      = $method;

    // Get the port for the WWW service
    $this->service_port = getservbyname('www', 'tcp');

    // Get the IP address for the target host
    $this->address = gethostbyname($this->host);

    // Create a TCP/IP socket
    $this->socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
    if (!$this->socket) {
      throw new RuntimeException("socket_create() failed: reason: " .
        socket_strerror(socket_last_error()));
    }

    // Set O_NONBLOCK flag
    socket_set_nonblock($this->socket);

    $this->conn_watcher = $this->http_client->getLoop()
      ->timer(0, 0., [$this, 'connect']);
  }

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

  private function freeWatcher(&$w) {
    if ($w) {
      $w->stop();
      $w = null;
    }
  }

  /**
   * Deallocates all resources of the request
   */
  private function close() {
    if ($this->socket) {
      socket_close($this->socket);
      $this->socket = null;
    }

    $this->freeWatcher($this->timeout_watcher);
    $this->freeWatcher($this->read_watcher);
    $this->freeWatcher($this->write_watcher);
    $this->freeWatcher($this->conn_watcher);
  }

  /**
   * Initializes a connection on socket
   * @return bool
   */
  public function connect() {
    $loop = $this->http_client->getLoop();

    $this->timeout_watcher = $loop->timer($this->timeout, 0., [$this, '_onTimeout']);
    $this->write_watcher = $loop->io($this->socket, Ev::WRITE, [$this, '_onWritable']);

    return socket_connect($this->socket, $this->address, $this->service_port);
  }

  /**
   * Callback for timeout (EvTimer) watcher
   */
  public function _onTimeout(EvTimer $w) {
    $w->stop();
    $this->close();
  }

  /**
   * Callback which is called when the socket becomes wriable
   */
  public function _onWritable(EvIo $w) {
    $this->timeout_watcher->stop();
    $w->stop();

    $in = implode("\r\n", [
      "{$this->method} {$this->resource} HTTP/1.1",
      "Host: {$this->host}",
      'Connection: Close',
    ]) . "\r\n\r\n";

    if (!socket_write($this->socket, $in, strlen($in))) {
      trigger_error("Failed writing $in to socket", E_USER_ERROR);
      return;
    }

    $loop = $this->http_client->getLoop();
    $this->read_watcher = $loop->io($this->socket,
      Ev::READ, [$this, '_onReadable']);

    // Continue running the loop
    $loop->run();
  }

  /**
   * Callback which is called when the socket becomes readable
   */
  public function _onReadable(EvIo $w) {
    // recv() 20 bytes in non-blocking mode
    $ret = socket_recv($this->socket, $out, 20, MSG_DONTWAIT);

    if ($ret) {
      // Still have data to read. Append the read chunk to the buffer.
      $this->buffer .= $out;
    } elseif ($ret === 0) {
      // All is read
      printf("\n<<<<\n%s\n>>>>", rtrim($this->buffer));
      fflush(STDOUT);
      $w->stop();
      $this->close();
      return;
    }

    // Caught EINPROGRESS, EAGAIN, or EWOULDBLOCK
    if (in_array(socket_last_error(), static::$e_nonblocking)) {
      return;
    }

    $w->stop();
    $this->close();
  }
}

/////////////////////////////////////
class MyHttpClient {
  /// @var array Instances of MyHttpRequest
  private $requests = [];
  /// @var EvLoop
  private $loop;

  public function __construct() {
    // Each HTTP client runs its own event loop
    $this->loop = new EvLoop();
  }

  public function __destruct() {
    $this->loop->stop();
  }

  /**
   * @return EvLoop
   */
  public function getLoop() {
    return $this->loop;
  }

  /**
   * Adds a pending request
   */
  public function addRequest(MyHttpRequest $r) {
    $this->requests []= $r;
  }

  /**
   * Dispatches all pending requests
   */
  public function run() {
    $this->loop->run();
  }
}


/////////////////////////////////////
// Usage
$client = new MyHttpClient();
foreach (range(1, 10) as $i) {
  $client->addRequest(new MyHttpRequest($client, 'my-host.local', '/test.php?a=' . $i, 'GET'));
}
$client->run();

Testing

Suppose http://my-host.local/test.php script is printing the dump of $_GET:

<?php
echo 'GET: ', var_export($_GET, true), PHP_EOL;

Then the output of php http-client.php command will be similar to the following:

<<<<
HTTP/1.1 200 OK
Server: nginx/1.10.1
Date: Fri, 02 Dec 2016 12:39:54 GMT
Content-Type: text/html; charset=UTF-8
Transfer-Encoding: chunked
Connection: close
X-Powered-By: PHP/7.0.13-pl0-gentoo

1d
GET: array (
  'a' => '3',
)

0
>>>>
<<<<
HTTP/1.1 200 OK
Server: nginx/1.10.1
Date: Fri, 02 Dec 2016 12:39:54 GMT
Content-Type: text/html; charset=UTF-8
Transfer-Encoding: chunked
Connection: close
X-Powered-By: PHP/7.0.13-pl0-gentoo

1d
GET: array (
  'a' => '2',
)

0
>>>>
...

(trimmed)

Note, in PHP 5 the sockets extension may log warnings for EINPROGRESS, EAGAIN, and EWOULDBLOCK errno values. It is possible to turn off the logs with

error_reporting(E_ERROR);

Concerning "the Rest" of the Code

I just want to do something like file_get_contents(), but not wait for the request to finish before executing the rest of my code.

The code that is supposed to run in parallel with the network requests can be executed within a the callback of an Event timer, or Ev's idle watcher, for instance. You can easily figure it out by watching the samples mentioned above. Otherwise, I'll add another example :)

ReactPHP async http client
https://github.com/shuchkin/react-http-client

Install via Composer

$ composer require shuchkin/react-http-client

Async HTTP GET

// get.php
$loop = \React\EventLoop\Factory::create();

$http = new \Shuchkin\ReactHTTP\Client( $loop );

$http->get( 'https://tools.ietf.org/rfc/rfc2068.txt' )->then(
    function( $content ) {
        echo $content;
    },
    function ( \Exception $ex ) {
        echo 'HTTP error '.$ex->getCode().' '.$ex->getMessage();
    }
);

$loop->run();

Run php in CLI-mode

$ php get.php