Chained List Boxes Not Filtering

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JScript.NET

PHP

MySQL

I have a series of three List Boxes, The first box is loading properly, however; the second and the third are loading but not filtering based on the previous selection. The tables are as such;

tblRestaurants
RestID
RestName

tblLocations
LocationID
RestID
CityID
AreaID

tblCities
CityID
CityName

tblAreas
AreaID
AreaName

I am using a function as well:

function createoptions($table , $id , $field , $condition_field , $value)
{
    $sql = sprintf("select * from $table WHERE $condition_field=%d ORDER BY $field" , $value);
    $res = mysql_query($sql) or die(mysql_error());
    if (mysql_num_rows($res) > 0) {
        while ($a = mysql_fetch_assoc($res))
        $out[] = "{optionValue: {$a[$id]}, optionDisplay: '$a[$field]'}";
        return "[" . implode("," , $out) . "]";
    } else

        return "[{optionValue: -1 , optionDisplay: 'No result'}]";
}

if (isset($_GET['tblRestaurants'])) {
    echo createoptions("tblLocations" , "CityID" , "Street" , "RestID" , $_GET['tblRestaurants']);
}


if (isset($_GET['AreaBox'])) {
    echo createoptions("tblAreas" , "AreaID" , "AreaName" , "AreaID = tblLocations.AreaID" , $_GET['tblLocations']);
}

die();

And this is to build the three Listboxes:

<form method = " post=">
<br mode=" hold=" />        
<select name = " restname=" id=" restid=">
<br mode=" -1=">--Select--</option>
<br mode=" tblrestaurants=", " cityid="><br mode=" tbllocations=", " areaid="><br mode=">