Unable to retrieve the sub categories - php

Question

Hello I have tried to make categories and sub categories and trying to call sub categories as --sub cat name because I placed the category and sub category in the same table is used nested option. But, that is not working for me.
Can anyone help me out this this categories are getting but unable to get sub categories
<select name="category" class="dropdown">
<?php
$query1 = $this->db->query('SELECT * FROM categories');
foreach($query1->result() as $cat_name) {
if($cat_name->cat_name == $cat_name->parent)
echo "<option>". $cat_parent = $cat_name->cat_name."</option>";
$query2 = $this->db->query("SELECT * FROM categories WHERE parent = '$cat_parent '");
foreach($query2->result() as $sub_cat) {
if($sub_cat->cat_name != $sub_cat->parent) {
echo "<option> --" . $sub_cat->cat_name . "</option>";
}
}
}
?>
</select>

Answer 1

Try following function which should work for you and it is in core php so,you have to implement yourself in to codeigniter
function fetchCategoryTreeList($parent = 0, $user_tree_array = '') {
global $con;
if (!is_array($user_tree_array))
$user_tree_array = array();
$sql = "SELECT * FROM `location` WHERE 1 AND `parent_id` = $parent ORDER BY id ASC";
$result=$con->query($sql);
if (mysqli_num_rows($result) > 0)
{
$user_tree_array[] = "<ul>";
while ($row =$result->fetch_object())
{
$user_tree_array[] = "<li>". $row->name."</li>";
$user_tree_array = fetchCategoryTreeList($row->id, $user_tree_array);
}
$user_tree_array[] = "</ul><br/>";
}
return $user_tree_array;
}
And call it as
$res = fetchCategoryTreeList();
foreach ($res as $r)
{
echo $r;
}
hope it will help you