How do you send a POST request using WizTools REST Client?

I'm trying to POST two values, that will be parsed by my PHP script, and echo a json-encoded response. These are two example values: 

$_POST['function'] = "sampleTestFunction";
$_POST['username'] = "Dom";

I have the url endpoint definitely working (if I hard-code the values, the json-encoded response shows), but I can't seem to figure out how to post the values from WizTools.

php rest post
Edit
Report