Example for Debug-Outputs in GuzzleHttp version 6+

GuzzleHttp6-Debug-Handler.php

<?php
  /**
   * @see: https://github.com/guzzle/guzzle/blob/master/UPGRADING.md#migrating-to-middleware
   * @see: http://docs.guzzlephp.org/en/stable/handlers-and-middleware.html
   **/

	$handler = \GuzzleHttp\HandlerStack::create();

	// watch request
	$handler->push(\GuzzleHttp\Middleware::mapRequest(function (\psr\Http\Message\RequestInterface $request) {
		printf("Request: %-8s %s\nHeaders-%s",$request->getMethod(),$request->getUri(),
			print_r(array_map(function($x) {return $x[0];}, $request->getHeaders()), true)
		);
		return $request;
	}));

	// watch response
	$handler->push(\GuzzleHttp\Middleware::mapResponse(function (\psr\Http\Message\ResponseInterface $response) {
		printf("Response: %3d %s\nHeaders-%s", $response->getStatusCode(), $response->getReasonPhrase(),
			print_r(array_map(function($x) {return $x[0];}, $response->getHeaders()), true)
		);
		return $response;
	}));


	$httpClient = new \GuzzleHttp\Client(array('handler' => $handler));
?>