Yes, slugger, I think you're right about the php (although php is not my thing).
I also agree that it isn't a huge difference. I've already implemented the form type post and it only ends up adding about 5 or 6 lines. I took me a little while to figure it out though. Posting just Json is more intuitive in C# - I think it's because posting straight JSON is more common for a standard JSON web api.
However, I was hoping it would be pretty easy to create another page in addition to request.php (so the existing clients would not break) - maybe something called "requestSimple.php"? I was hoping it just might make it easier for future client devs.
If it's not practical or worthwhile, that's cool. It's just a suggestion.
Thanks for your input