Our ecommerce operation require tracking of Google Analytics data, and submitting analytic data with the form data for submission into the Pardot. This will help us track clicks and conversions of advertisement dollars we spent on various channels. For some reason, the analytics data from the landing pages failed to make it into our Pardot account so I had to troubleshoot this problem. Since this is my second time troubleshooting same problem, I would like to use this to document troubleshooting steps for future reference. If you're not using Pardot, the first 2 steps are all you needed to diagnose your GA problem.
3. If you use Browser Emulator such as Snoopy to submit the data, the cookie data is properly assigned to Snoopy cookies via associative array (instead of an object). We use Snoopy to submit the form in the background since Pardot takes several seconds to process the form submission. Also, if you're encoding and decoding json_encode or json_decode, you may want to verify that the magic_quote_gpc is turned off in php.ini file.
4. For GA data to be auto populated within Pardot, you'll have to install GA connector within Pardot. For instruction on installing GA connector, you may want to consult Pardot documentation.