wordpress dependent dropdownlist using post type is not working

PHP

Select Doctors
‘doctors’,
‘posts_per_page’ => -1,
‘meta_query’ => array(
array(
‘key’ => ‘dptmnt’,
‘value’ => $dpt,
‘compare’ => ‘LIKE’
),
‘order’ => ‘ASC’
),
);
$events = new WP_Query($args);
while ($events->have_posts()):
$events->the_post();
?>
“>

HTML

Select Department
‘dpt’,
‘posts_per_page’ => -1,
‘orderby’ => ‘title’,
‘order’ => ‘ASC’
);
$events = new WP_Query($args);
while ($events->have_posts()):
$events->the_post();
?>
“>

AJX

$(function () {
$(“select[name=”dp”]”).change(function () {
var str = “”;
$(“select[name=”dp”] option:selected”).each(function () {
str += $(this).text() + ” “;

});

jQuery.ajax({
type: “POST”,
data: $(“form#a”).serialize(),

success: function (data) {
// alert(data);
// jQuery(“.res”).html(data);

$(‘#doc’).html(data);

}
});
var str = $(“form”).serialize();
// $(“.res”).text(str);
});
});

This work for me