JQuery :: Autocomplete Does Not Pass Parameter To PHP Script

I'm having a lot of difficulty getting an ajax option in Autocomplete to pass a variable value to a php script. I started with an Autocomplete that works well sending parameters to geonames.com and retrieving responses, but as I changed: type to POST, dataType to json, and changed the data option, it no longer works. Despite a lot of searching, I can't find the problem. The php seems to get an object, but it seems to be empty. Firebug is not helping much or I don't know how to use it for this kind of debugging. I get no error messages.

Here's the jQuery:
$('stateProvince').autocomplete({
source: function( request, response ){
$.ajax({
url: "getStateProvince.php",
type: "POST", // a jQuery ajax POST always transmits in utf-8 characters
data: {countryAbbrev: $('input[name=country]:checked').val()}, //correct value here dataType: "json",
success: function( countryData ){
response( $.map( countryData.getStateProvince, function( item ){
return{
label: item.name + (item.abbrev ? ", " + item.abbrev : ""),
value: item.abbrev
}}));
}});
},
minLength: 2
});

And here's a bit of php test code to see if the value is passed in:
<?php
$country=$_POST['countryAbbrev'];
echo "hello world, country is {$country} <br>"; //test for contents of POST
print_r($_POST);
?>