Proxy Google Analytics traffic using sendHitTask

send-hit-task.js

ga('create', 'UA-XXXXXX-Y', 'auto');
// Insert this function after the property is created and before the pageview is sent.
ga(function(tracker) {
  tracker.set('sendHitTask', function(model) {
    payload = model.get('hitPayload');
    var xhr = new XMLHttpRequest();
    xhr.open('POST', 'https://yourdomain.com/your-proxy-file.php', true);
    xhr.send(payload);
  });
ga('send', 'pageview');