jQuery Autocomplete via PHP error

I’m trying to get an autocomplete working for a website I’m building for my company, but I can’t seem to get the jQuery function to execute. The website is build on top of WordPress.

The input line:

<strong>Customer: </strong> <input type='text' name='cust' id='cust'>

The autocomplete:

<script type='text/javascript'>
jQuery('#cust').autocomplete({
    source : "Scripts/cust_search.php",
    minLength:1 
});

And cust_search.php:

<?
$term = trim(strip_tags($_GET[ "term" ]));

$a_json = array ();
$a_json_row = array ();

if ($companies = $panther->get_results("SELECT Cust_ID, Cust_Name FROM Customer LIKE '%$term%' ORDER BY Cust_Name ASC;")) {
while ($row = mysqli_fetch_array($companies)) {
    $a_json_row ["id"]=$panther->escape($row['Cust_ID']);
    $a_json_row ["value"]=$panther->escape($row['Cust_Name']);
    $a_json_row ["label"]=$panther->escape($row['Cust_Name']);

    array_push($a_json, $a_json_row);
}
}

echo json_encode( $a_json );
?>