If you are getting those issues, you are not using the files from github. Go to
https://github.com/lat9/one_page_checkout, click on the Green CODE button and download the zip.
There are some changes in the admin files that need to be made for WebPay to work with some shipping modules AND some changes in files inside the includes folder to fix the var_export problem.
The errors you reported were fixed with
the fix for #328 and ARE included in the download zip file.
You can fix the third var_export
mentioned in the Pull Request either before or after you upload all the files. If you don't do the fix, you will get yet another var_export error for line 784 of includes/cllasses/observers/class.checkout_one_observer.php.
You can just overrite the existing files on your site and it wil work fine.
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