Dynamic datepicker disappearing

I have a PHP function that gets dates from a database that need to be highlighted and disabled on the date picker.

I have a function that works if I declare the dates like var disabledDates = ["12-02-2015"]; but when I try using var disabledDates = <?php echo json_encode($date); ?>; the date picker disappeared from the screen. Is there a reason why this is happening?

Below is my code:

<script>
    function unavailable(date) {
        var dmy = date.getDate() + "-" + (date.getMonth()+1) + "-" + date.getFullYear(); console.log(dmy);
        var disabledDates = <?php echo json_encode($date); ?>;

        if ($.inArray(dmy, disabledDates) < 0) {
            return [true,"",""];
        } else {
            //the second parameter you can set your css class
            return [false,"red","Day unavailable"];
        }
    }

    $('#datepicker').datepicker({
        altField : '#hiddenFieldID',
        format: 'dd-mm-yyyy',
        changeMonth:true,
        minDate: 14,
        beforeShowDay: unavailable //here it is
    });
</script>

PHP:

$fullybooked = getfullybookeddays();
  $dates = array();
  $i = '0';

  while($row = mysql_fetch_assoc($fullybooked)){ 

  $dates[$i] = str_replace('/', '-', $row['hdate']);
  $i++;

  }

  $date_list = '["' . implode('", "', $dates) . '"]';