It's working :)
$("#quick-search").autocomplete('/includes/search.php',{ width: 300, scroll: false, dataType: "json", parse: function(data){ return $.map(data, function(row){ return{ data: row, value: row.location_id, result: row.location } }); }, formatItem: function(result){ return result.location; } }).result(function(e, item) { $('#location_id').attr('value',item.location_id); });