Fill Drop down On select Of Drop down

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>'; 
        }
    }

}