How to iterate for objects with indeterminate nesting

Question

I have a class called Document. Each Document may be the son of a Document or Parent of a Document. Each Document can only have one Parent and can have countless children.

I’m trying to write a function Document->parentLevel() to find out how many levels of hierarchy (maximum) exist below this Document.

For example:

                     Doc1 
       Doc2          Doc3         Doc4
   Doc5    Doc 6
Doc7

When rotating Doc1->parentlevel() the function would return 3, as the largest number of hierarchical levels below it is 3 (Doc2->Doc5->Doc7).

Objects have a function Document->hasChildren() returning true or false if the object has children and a function Document->children() that returns a array with the children of that object.

My code so far:

public function parentLevel($startLevel = 0)
    {
        $level = $startLevel;
        $active = $this;
        while ($active->hasChildren()) {
            $level++;
            foreach ($children as $child) {
                if ($child->hasChildren()) {
                    $level2 = $child->parentLevel();
                    if ($level2 > $level) {
                        $level = $level2;
                    }
                }
            }
        }
        return $level;
    }

Answer 1

If you don’t need to know which nodes are part of the bigger business, just do:

public function parentLevel ()
{
    $level = 0;

    if ($this->hasChildren())
    {
        $childrenLevels = [];

        foreach($this->children() as $child)
        {
            $childrenLevels[] = $child->parentLevel();
        }

        $level = max($childrenLevels) + 1;
    }

    return $level;
}

See working on Ideone.

Basically, if the knot has children, it looks for the child that has the highest value of parentLevel and increments by 1, otherwise returns 0.