Fill Drop down On select Of Drop down - php

Question

how to fill dropdown values on selection of multiple dropdown.for example i have following Dropdown list.
On select of second dropdown i wants to fill Third Dropdown With Single selection How can i do. ?
My current code for this is as follow.
//CALL FOR SECOND DROPDOWN
$(document).ready(function(){
$('#select4').on('change',function(){
var subcatgoryId = $(this).val();
console.log(subcatgoryId);
if(subcatgoryId){
$.ajax({
type:'POST',
url:'ajax_load_specification.php',
data:{subcatgoryId: subcatgoryId},
success:function(html){
alert(html);
//$('#select5').html(html);
//$('#loading1').css("display","none")
},
error: function (jqXHR, exception) {
alert("Got Some Errore");
}
});
}else{
$('#select5').html('<option value="">Select Category first</option>');
}
});
});
and php code is as follow
if(isset($_POST["subcatgoryId"]) )
{
$subcategory = explode(',', $_POST["subcatgoryId"]);
print_r($_POST["subcatgoryId"]);
foreach ($subcategory as $key => $value)
{
echo $key;
echo "<br>";
$query1 = "SELECT * FROM m_subcategory WHERE id = ".$item." ";
$query1 = $conn->query($query1);
$query1 = $query1->fetch_object();
if($query1){
$id = $query1->id;
$name = $query1->name;
echo '<option value="'.$id.'">'.$name.'</option>';
}else{
echo '<option value="">We Get Empty Category</option>';
}
}
}

Answer 1

Just Use For Loop And it starts working
if(isset($_POST["subcatgoryId"]) )
{
$subcategory = $_POST["subcatgoryId"];
$len=count($subcategory);
for ($i=0; $i < $len; $i++) {
$query1 = "SELECT * FROM m_subcategory WHERE id = ".$subcategory[$i]." ";
$query1 = $conn->query($query1);
$query1 = $query1->fetch_object();
if($query1){
$id = $query1->id;
$name = $query1->name;
echo '<option value="'.$id.'">'.$name.'</option>';
}else{
echo '<option value="">We Get Empty Category</option>';
}
}
}