Feature: #70056 - Added PHP library "Guzzle" for HTTP Requests within TYPO3

Description

The PHP library Guzzle has been added via composer dependency to work as a feature rich solution for creating HTTP requests based on the PSR-7 interfaces already used within TYPO3.

Guzzle auto-detects available underlying adapters available on the system, like cURL or stream wrappers and chooses the best solution for the system.

A TYPO3-specific PHP class called TYPO3\CMS\Core\Http\RequestFactory has been added as a simplified wrapper to access Guzzle clients.

All options available under $TYPO3_CONF_VARS[HTTP] are automatically applied to the Guzzle clients when using the RequestFactory class. The options are a subset to the available options on Guzzle (http://docs.guzzlephp.org/en/latest/request-options.html) but can further be extended.

Existing $TYPO3_CONF_VARS[HTTP] options have been removed and/or migrated to the new Guzzle-compliant options.

A full documentation for Guzzle can be found at http://docs.guzzlephp.org/en/latest/.

Although Guzzle can handle Promises/A+ and asynchronous requests, it currently acts as a drop-in replacement for the previous mixed options and implementations within GeneralUtility::getUrl() and a PSR-7-based API for HTTP requests.

Impact

The existing TYPO3-specific wrapper GeneralUtility::getUrl() now uses Guzzle under the hood automatically for remote files, removing the need to configure settings based on certain implementations like stream wrappers or cURL directly.

The RequestFactory class can be used like this:

// Initiate the Request Factory, which allows to run multiple requests
/** @var \TYPO3\CMS\Core\Http\RequestFactory $requestFactory */
$requestFactory = GeneralUtility::makeInstance(\TYPO3\CMS\Core\Http\RequestFactory\RequestFactory::class);
$url = 'https://typo3.com';
$additionalOptions = [
   // Additional headers for this specific request
   'headers' => ['Cache-Control' => 'no-cache'],
   // Additional options, see http://docs.guzzlephp.org/en/latest/request-options.html
   'allow_redirects' => false,
   'cookies' => true
];
// Return a PSR-7 compliant response object
$response = $requestFactory->request($url, 'GET', $additionalOptions);
// Get the content as a string on a successful request
if ($response->getStatusCode() === 200) {
   if ($response->getHeader('Content-Type') === 'text/html') {
      $content = $response->getBody()->getContents();
   }
}

Extension authors are advised to use the RequestFactory class instead of using the Guzzle API directly in order to ensure a clear upgrade path when updates to the underlying API need to be done.