How Can I Perform Asynchronous GET Requests in PHP?

Asynchronous GET Requests in PHP: A Detailed Guide

Introduction

Performing asynchronous GET requests in PHP allows your script to initiate a request to a remote server without blocking the current execution flow. This is highly beneficial for web applications that need to send numerous requests without stalling user interactions.

Using file_get_contents() for Asynchronous Requests

file_get_contents() is a built-in PHP function that can be utilized for both synchronous and asynchronous GET requests. By default, it behaves synchronously, blocking the script until the request is complete. However, providing an optional context argument allows for asynchronous operation.

• Synchronous Request:

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

• Asynchronous Request:

  $context = stream_context_create([
    'http' => [
        'ignore_errors' => true
    ]
  ]);
  
  $output = file_get_contents('http://www.example.com/', false, $context);

Using fsockopen() for Truly Asynchronous Requests

For situations where even the asynchronous behavior of file_get_contents() is undesirable, fsockopen() offers a lower-level approach to achieving true asynchronicity. This function allows for direct socket communication.

• Asynchronous Request Using fsockopen():

  function curl_post_async($url)
  {
    // 1. Parse URL
    $parts = parse_url($url);
  
    // 2. Open Socket
    $fp = fsockopen($parts['host'],
        isset($parts['port']) ? $parts['port'] : 80,
        $errno, $errstr, 30);
  
    // 3. Construct Request
    $out = "GET " . $parts['path'] . " HTTP/1.1\r\n";
    $out .= "Host: " . $parts['host'] . "\r\n";
    $out .= "Connection: Close\r\n\r\n";
  
    // 4. Send Request and Close Socket
    fwrite($fp, $out);
    fclose($fp);
  }

This function fires off the GET request immediately, without waiting for a response, and returns control to the caller. It is essential to note that using fsockopen() requires a more hands-on approach compared to file_get_contents().

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