How to track pdf downloads from properly (Google Analytics)?

On my website, there is a possibility to download pdfs. Until here, everything is fine.

Now, I would like to track the pdf downloads. This can be done by using Google Analytics Events in the link of the pdf:

<a onclick="var that=this;_gaq.push(['_trackEvent','Download','PDF',this.href]);setTimeout(function(){location.href=that.href;},400);return false;" href="pdfs/my-file.pdf">Download my file</a>

The problem is that if somebady will download the pdf from a search engine, not directly from the website, this will not be tracked.

Do you know a proper method on how to track that?

Should I implement something on the server side when I am rendering the pdf, that will trigger a GA event?

Thank you in advance.

Solution

Here is one solution I just found:

php-ga Google Analytics for PHP

With php-ga, there is a possibility to simulate pageviews on the server side. So, now for me, when somebody downloads a pdf, I am also calling this code:

        // Initilize GA Tracker
        $tracker = new GoogleAnalytics\Tracker('UA-5824718-6', 'mdpi.com');

        // Assemble Visitor information
        // (could also get unserialized from database)
        $visitor = new GoogleAnalytics\Visitor();
        $visitor->setIpAddress($_SERVER['REMOTE_ADDR']);
        $visitor->setUserAgent($_SERVER['HTTP_USER_AGENT']);
        $visitor->setScreenResolution('1024x768');

        // Assemble Session information
        // (could also get unserialized from PHP session)
        $session = new GoogleAnalytics\Session();

        // Get filename from the previous request
        $filename = parse_url(urldecode($_SERVER['REQUEST_URI']), PHP_URL_PATH);

        // Assemble Page information
        $page = new GoogleAnalytics\Page($filename);
        $page->setTitle($filename);

        // Track page view
        $tracker->trackPageview($page, $session, $visitor);

        $this->downloadFile($file, 'application/pdf');

The only problem I will have to fix is how to filter bots (Robots)...