为什么这个autosuggest不起作用？

I've done some research and followed a tutorial exactly, with minor changes, but I can't seem to get this to work. No dropdown appears. Can you look at the code and tell me what is not happening?

<div class="ui-widget">
    <label for="skills">Skills: </label>
    <input id="skills">
</div>
<script>
$(function() {
    $( "#skills" ).autocomplete({
         width:448,
         delimiter: /(,|;)\s*/,
         lookup: <?php echo "'autocomplete(#skills)'" ?>
    });
});
</script>

<?php     
$servername = 'localhost';
$username = 'xx';
$password = 'xx';

$con = mysql_connect($servername,$username,$password);
mysql_select_db('c9', $con);

function autocomplete($inputName){
    $searchTerm = $_GET[$inputName];
    $query = mysql_query("SELECT * FROM clients WHERE fname LIKE '%".$searchTerm."%' ORDER BY fname ASC");
    while ($row = mysql_fetch_array(MYSQL_ASSOC)) {
        $data[] = $row['fname'];
    }
    //return json data
    echo json_encode($data);
}

?>