Datepicker不接受数据库中的日期

I'm trying to get a database date value to display in the datepicker. I'm also converting from the yyyy-mm-dd database format to the datepicker format, but it's not display the value in my datepicker. If I echo the date value separately, it is displaying the correct value, but not inside the datepicker only in the form.

Here is my datepicker function.

$(document).ready(function() {  //display calender
    $("#datepicker").datepicker();
    $('#datepicker').datepicker( 'option', { changeYear: true } );
    $('#datepicker').datepicker( 'option', { changeMonth: true } );
    $('#datepicker').datepicker( 'option', { yearRange: '1950:2015' } );
    $( "#datepicker" ).datepicker('option', 'dateFormat' , 'dd-mm-yy'); 
});

input  type="text" id="datepicker" name="datepicker" value="php if(isset($dob)) echo $dob;?>"

$dob is fetched from the database and carries the correct value if echoed. Can anyone help?