PHP script to process BITPAY ipn calls and run another function

We are working to accept bitcoins as an extra payment method, however, we need to build a script to receive BITPAY (the processor we are going to use) IPN calls and verify everything and then run a given function (already built, which is the function that actually processes the order). We already got their PHP library and run some tests but failed to process the IPN while we are receiving the IPN call. The PHP library is here: [login to view URL] More details provided to the winner.