禁用jQuery UI日期选择器日期

I am trying to disable dates in a jQuery UI Date Picker, it works when I hard code the dates in to the variable in the JS file as follows:

var bookedDays = ["2015-3-7","2015-3-8","2015-3-15"];

In my PHP file I have:

<?php
$testing = "SELECT fromdate, todate FROM messages WHERE listing_id = '".$_GET['listingid']."'";
        $resulttesting = mysql_query($testing) or die(mysql_error() . "<br>" . $testing);
        while ($rowtesting = mysql_fetch_assoc($resulttesting)) 
{
    $from = $rowtesting['fromdate'];
    $to = $rowtesting['todate'];

}

$start_time = strtotime($from);
$end_time = strtotime($to);
$date_list = array($from);

$current_time = $start_time;

while($current_time < $end_time) {
    //Add one day
    $current_time += 86400;
    $date_list[] = date('Y-m-d',$current_time);
}
//Finally add end date to list, array contains all dates in order
$date_list[] = $to;
$date_list_res = '["' . implode('","', $date_list) . '"]';

print_r ($date_list_res);

?>
<script type="text/javascript">
    var bookedDays = <?php echo json_encode($date_list_res); ?>;
</script>

When I run a console.log in the JS file for the variable bookedDays I get ["2015-03-05","2015-03-06","2015-03-07","2015-03-08","2015-03-08"] output which is read from the database which is correct but these dates are not disabling in the date picker. Does anybody know where I'm going wrong?

Instead of

<?php echo json_encode($date_list_res); ?>;

Type just

<?php echo $date_list_res; ?>;

Everything should be dandy.