PHP - Moved: $_get From Iframe Child

Hi I am trying to create a hierarchy array from our mysql database.

What i have so far is:

//instantiate DB & connect
$database = new Database();
$db = $database->connect();

//instantiate question object

$question = new Question($db);

//query
    $results = $question->read(); 
   
      //check for data
    if ($results) {

     $question_arr['questions'] = array();
     $child_arr = array();
     
    while ($row = $results->fetch(PDO::FETCH_ASSOC)) {
        
        array_push($question_arr['questions'], $row);

        $question_arr['questions'][] = buildTree($row);

    }
        print_r($question_arr['questions']);
} else {
    echo json_encode(array('message'=>'nothing here!.'));
}


function buildTree($child) {
    $branch = array();
   foreach ($child as $row) {
    
    $childresults = $question->read_children($row['parentid']); 
    
           while ($childrow =$childresults->fetch(PDO::FETCH_ASSOC)) {
             
            $children = buildTree($childrow);

            if ($children) {
             $row['children'] = $children;
            }
         
            $branch[] = $childrow;
        }
    }
   //}
    return $branch;
}

in my Questions.php file:

<?php
class Question{
    private $conn;
    public $id;
    public $childid;
    public $parentid;
    public $question;
    public $pageid;
    public $numclicks;
    public $typeid;
    public $date_created;

 
     // Constructor with DB
     public function __construct($db) {
        $this->conn = $db;
      }

   public function read() {
        //create query(sql statement)
      $query = 'SELECT id as parentid, question, pageid, typeid,numclicks,date_created from ct_questions';
      // Prepare statement
      $stmt =$this->conn->prepare($query);
      // Execute query
      $stmt->execute();
      return $stmt;
    }

public function read_children($parentid)
{
//This is from a View I created in Mysql
    $query = 'SELECT parent_question, parentid, parent_pageid, child_question, childid, child_pageid from ct_vquestion_parent_child_lookup where parentid='.$parentid.'';
    // Prepare statement
    $stmt = $this->conn->prepare($query);
  
    // Execute query
    $stmt->execute();
   
    return $stmt;
}
}

the current errors i am getting a

<br /> <b>Notice</b>: Undefined variable: question in <b>C:\htdocs\api\questions\read.php</b> on line <b>41</b><br /> <br /> <b>Fatal error</b>: Uncaught Error: Call to a member function read_children() on null in C:\htdocs\api\questions\read.php:41 Stack trace: #0 C:\htdocs\api\questions\read.php(28): buildTree(Array) #1 {main} thrown in <b>C:\htdocs\api\questions\read.php</b> on line <b>41</b><br />