Ugh I cannot even explain the solution because of this forum's HTTP rules. Hence the spaces in these URLs... And even once I correct them, the buggy forum software doesn't recognize I've done it. I have to start over.
So for anyone else getting this, I managed to fumble through it. Using the 'ptv2' site I was able to send my POST without problem. That made me think the problem was on the server side. Then I read online about how people were seeing POSTs converted to GETs when the data was empty - or when there was a redirect. What solved it for some people was changing 'www .mysite.com' to 'mysite.com'. I tried this, but it did not work for me. However, it may have been one step in the solution, something I needed to do.
I confirmed on the PHP side that it did indeed think it was getting a GET and not a POST. But why though...
I noticed that when I went to 'http : //mysite.com', in the browser it was being converted to 'https : //mysite.com'.
That was the solution. I needed to change 'http' to 'https' (and probably, " www .blah.com" to "blah.com").