Question

Basically, we want to A/B test 2 different page layout headers. There are some structural differences (it’s not just switching out the CSS). We also don’t want to wait for Google to flip the coin to determine which variation the visitor should see; instead, we want to choose the variation server-side and avoid a page redirect.

The code below does what I hoped it would; the UTMX cookie it generates looks identical to the one that the Google-supplied javascript would generate if I didn’t omit it from the head tag.

Server-side PHP code:

public function setUtmxCookie($cookieName, $experimentsString)
{
    $domainHash = $this->getDomainHash($_SERVER['SERVER_NAME']);
    $cookieVal = $domainHash . $experimentsString;
    $expire = time() + 60 * 60 * 24 * 30;
    $domain = '.' . $_SERVER['SERVER_NAME'];
    setrawcookie($cookieName, $cookieVal, $expire, '/', $domain);
}

private function getExperimentsFromUtmxCookie($cookieName)
{
    if (isset($_COOKIE[$cookieName])) {
        $cookieVal = $_COOKIE[$cookieName];
        $experimentsArray = array();
        $experimentMatches = preg_split('/\./', $cookieVal);
        $domainHash = array_shift($experimentMatches); //remove the first item.  All that will remain in $experimentMatches is an array of experimentIds with their combos.
        foreach ($experimentMatches as $m) {
            $segments = preg_split('/:/', $m);
            $experimentsArray[$segments[0]] = $segments[1];
        }
        return $experimentsArray;
    }
    return array();
}

private function getExperimentsString($cookieName, $experimentId, $variation)
{
    $experiments = $this->getExperimentsFromUtmxCookie($cookieName);
    $experiments[$experimentId] = $variation;
    $experimentsString = '';
    foreach ($experiments as $key => $val) {
        $experimentsString .= '.' . $key . ':' . $val;
    }
    return $experimentsString;
}

Why isn’t my Google Analytics Content Experiments dashboard showing any visitors to my experiment, then? Did I set the utmx cookie imperfectly? Other than setting the UTMX cookie, is GACE looking for anything else?

Answer 1

We’ve been using a totally different approach for the past couple months: Amazon load-balancers (AWS ELB) plus Google Analytics (not Content Experiments). (See my comment above.) As we hoped, it has greatly improved our experience with merging back to trunk.

_gaq.push(['_setCustomVar', 2, varName, varValue, 2]);//https://developers.google.com/analytics/devguides/collection/gajs/gaTrackingCustomVariables
_gaq.push(['_trackPageview']);//This must come AFTER the setCustomVar
//varName should be whatever you want to call the experiment
//varValue should be something like "original" for the original and "variation" for the variation.  We just use "trunk" and [name of variation branch].

Obvious drawbacks are that Google doesn’t do the math for us (telling us whether the variation has statistically significantly outperformed the original) and that we can’t easily run multiple experiments at once. We also wouldn’t be able to have many variations (we’d need to add more load-balanced instances than we’d want).

But for our purposes (e.g. given how important it is to us not to have a page refresh), it has worked better than other approaches.