How to return object value from JS to PHP via exec + phantom.js?

Question

JavaScript

Good day, colleagues.
The essence of the question is as follows, let's say there is a js file:

var webPage = require('webpage');
var page = webPage.create();

page.open('https://vk.com/', function (status) {
    var cookies = page.cookies;
    phantom.exit();
});

This code is sent to phantom.js for execution via php:

$command =  'js\phantomjs.exe ' . 'src.js';
exec($command, $output);

var_dump(($output));

Question. What is the most correct way to pass the cookie object in PHP to the output variable?
Thank you.