PxPay request returnUrl encoding.

[dm1tr1]

Changes from the closed PR #38 also appear in the merged PR #33.

[mediabeastnz]

I think we're seeing this issue with responses returning the encoded data.
For example the response we get back is encoded like & which has potential to break systems that rely on GET parameters.

[judgej]

Looks like htmlentities() function here. That's wrong. The getReturnUrl() function should return a simple URL string, not encoded for any particular use.

Until this is fixed, you can reverse it using html_entity_decode() (but maybe check for the presence of & entites first.