pass a string from jQuery to php

pass a string from jQuery to php

In a tiered Autocomplete, I need to pass a string from the first selection into a php script to limit the search in the second tier Autocomplete. After much research, I can't get the string to the php.  All files are in the same directory.

Here's the jQuery:

        //set countryFilter for the 2nd tier to select stateProvince from only the country selected in the 1st tier
        countryFilter="countryAbbrev=" + $('input[name=country]:checked').val();     //eg. countryAbbrev=US
        $('stateProvince').autocomplete
        ({
            source: function( request, response )
            {
                $.ajax(
                {
                    url: "getStateProvince.php",                   
                    type: "POST",  
                    data: countryFilter,
                    dataType: "json",   //expect returned data to be in json format                                       
                    success: function( return_arr )
                    {
                        response( $.map( return_arr.getStateProvince, function( item )
                        {
                            return{
                                    label: item.name + (item.abbrev ? ", " + item.abbrev : ""),
                                    value: item.abbrev
                                   }
                        }));
                    }
                });               
            },
            minLength: 2
        });

Here's the relevant php - intended to match up countryAbbrev, get the string and print a test. I have also tried using countryFilter and it does not work either.

<?php
$country=$_POST['countryAbbrev'];
print "country is {$country} <br>";

Currently, the php prints country is,  but no variable.