AJAX response logging with Symfony Panther

index.php

<?php
use Symfony\Component\Panther\Client;

require 'vendor/autoload.php';

$client = Client::createFirefoxClient();
try {
	$crawler = $client->request('GET', 'https://www.example.com/');

	$client->executeScript(/** @lang JavaScript */ 'function addXMLRequestCallback(callback) {
		var oldSend, i;
		if(XMLHttpRequest.callbacks) {
			XMLHttpRequest.callbacks.push(callback);
		} else {
			XMLHttpRequest.callbacks = [callback];
			oldSend = XMLHttpRequest.prototype.send;
			XMLHttpRequest.prototype.send = function() {
				for(i = 0; i < XMLHttpRequest.callbacks.length; i++) {
					XMLHttpRequest.callbacks[i](this);
				}
				oldSend.apply(this, arguments);
			};
		}
	}
	addXMLRequestCallback(function(xhr) {
		//do nothing
	});
	window.ajax = [];
	addXMLRequestCallback(function(xhr) {
		window.ajax.push(xhr);
	});');

	//click some button on the page to trigger the ajax call
	$crawler->filter('button')->click();

	//wait a predetermined amount of time for the process to complete
	sleep(1);

	/** @noinspection JSUnresolvedVariable */
	$xhrs = $client->executeScript(/** @lang JavaScript */ 'return window.ajax;');
	foreach($xhrs as $xhr) {
		echo "From {$xhr['responseURL']} came this response:\n{$xhr['response']}\n";
	}
} catch(\Throwable $e) {
	$filename = tempnam(sys_get_temp_dir(), 'screenshot_'); //will be png without the suffix
	$client->takeScreenshot($filename);
	echo "{$e->getMessage()} (Check $filename for screenshot)\n";
}
$client->quit();
$client->getBrowserManager()->quit();