jQuery Forum

Erik,
A tutorial that should help is:
http://www.jensbits.com/2010/03/29/jquery-ui-autocomplete-widget-with-php-and-mysql/

Check your php output to ensure your code constructs proper JSON.  Use JSONLint.com to test the output

Use Firebug for debugging.  Its console will show you the json passing to and from the server.

Here's working jQuery code that shows how to send a filter off to php and process the JSON coming back.

        //set the country filter for the 2nd tier to select stateProvince from only the country selected in the 1st tier
        $("#stateProvince").autocomplete
        ({
            source: function (request, response)
            {  
                //Pass the selected country to the php  to limit the stateProvince selection to just that country
                $.ajax(
                {
                    url: "getStateProvince.php",
                    data: {
                            term: request.term,
                            country: $('input[name=country]:checked').val(),    //Pass the selected countryAbbreviation
                          },
                    type: "POST",  // POST transmits in querystring format (key=value&key1=value1) in utf-8
                    dataType: "json",   //return data in json format
                    success: function (data)
                    {
                        response($.map( data, function (item)
                        {
                            return {
                                    label: item.stateName,
                                    value: item.name,
                                    abbrev: item.stateAbbrev,
                                    }
                        }));
                    }
                });
            },
            select: function (event, ui)
            {   "use strict";
                $(this).val(ui.item.value);
                $("#hiddenState").val(ui.item.abbrev);  //put the stateProvince abbrev'n in the hidden input box
                //alert("|" + $("#hiddenState").val() + "|3rd");
                //reset city to null when user changes stateProvince selection
                $("#city3").val(null);
                //reset neighborhood to null when user changes stateProvince selection
                $("#neighborhood3").val(null);
            },
            minLength: 1
        });

This retrieves the data from the input.

1. $somevariablename = $_GET["term"];

https://forum.jquery.com/topic/autocomplete-remote-source-using-php-sql-server-get-q-or-term-problem

 
A request object, with a single property called "term", which refers to the value currently in the text input. For example, when the user entered "new yo" in a city field, the Autocomplete term will equal "new yo".

- from http://jqueryui.com/demos/autocomplete/#default