Implementing a tree using PHP

So far, you have learned about different properties of a tree data structure. If we compare a tree data structure with a real-life example, we can consider our organization structure or family tree to represent the data structure. For an organization structure, there is one root node that can be the CEO of the company, followed by CXO-level employees, followed by other level employees. Here, we are not restricting any degree for a particular node. This means a node can have multiple children. So, let's think of a node structure where we can define the node property, its parent node, and its children nodes. It might look something like this:

class TreeNode { 

    public $data = NULL; 
    public $children = []; 

    public function __construct(string $data = NULL) { 
      $this->data = $data; 
    } 

    public function addChildren(TreeNode $node...