sub category menu php

gistfile1.txt

<?php
	$server = "localhost";
	$username = "xxxx";
	$pasword =  "xxxx";
	$dbName = "xxxx";

	$conn = new mysqli($server, $username, $pasword, $dbName);
	if($conn->connect_error) {
		die('Connection Error'. $conn->connect_error);
	}
	//echo "Connection Successfully";

		
		// SELECT LIST
	function categoriesTree($parent_id = 0, $sub_mark = '') {
		global $conn;

		$query = $conn->query("SELECT * FROM category WHERE parent_id = $parent_id ORDER BY name ASC");
		if ($query->num_rows > 0) {
			while ($row = $query->fetch_assoc()) {
				echo '<option value="'.$row['id'].'">'.$sub_mark.$row['name'].'</option>';
				categoriesTree($row['id'], $sub_mark.'---');
			}
		}
	}
		// UL LIST
	
	function fetchCategoryTreeList($parent = 0, $user_tree_array = '') {
 	global $conn;

    if (!is_array($user_tree_array))
    $user_tree_array = array();
	 
	  $sql = $conn->query("SELECT `id`, `name`, `parent_id` FROM `category` WHERE 1 AND `parent_id` = $parent ORDER BY id ASC");
	  
	  if ($sql->num_rows > 0) {
	     $user_tree_array[] = "<ul>";
	    while ($row = mysqli_fetch_object($sql)) {
		  $user_tree_array[] = "<li>". $row->name."</li>";
	      $user_tree_array = fetchCategoryTreeList($row->id, $user_tree_array);
	    }
		$user_tree_array[] = "</ul>";
	  }
	  return $user_tree_array;
	}


 ?>
 <select name ="categories">
 	<?php categoriesTree(); ?>	
 </select>
 <ul>
<?php
  $res = fetchCategoryTreeList();
  foreach ($res as $r) {
    echo  $r;
  }
?>
</ul>