PayPal IPN API PHP Programming + Analtyics eCommerce integration with listener

Background: Current script allows user to SUBSCRIBE to our services either 3, 6 or 12 months recurring billing and IPN listener inserts the users information into the relevant databases which is stored in the custom filled and passed to PayPal. The following tasks need to be carried out: - Fix PayPal IPN listener as currently its inserting twice, instead of once - Modify the script so that when the user is re-billed at the end of the first billing cycle, his subscription end date is updated and the transaction is inserted into the database - Implement Google Analytic eCommerce into the listener to record all sales and transactions, the javascript code doesn't work. I'm assuming the PHP Google Analytics API would have to be used.