B-Tree in PHP test implementation

btree.php

<?php

declare(strict_types=1);

final class Node{
    
    public static function buildTree(int $size, ?Node $node = null) : self{
        $node ??= new Node();
        $node->entries[0] =  new Node();
        $node->entries[1] = new Node();
        if($size <= 2){
            static $i = 0;
            $node->entries[0] = $i++;
            $node->entries[1] = $i++;
            return $node;
        }

       $size /= 2;
       self::buildTree($size, $node->entries[0]);
       self::buildTree($size, $node->entries[1]);
       return $node;
    }
    
    public array $entries;
    
    public function __construct(array $entries = []){
        $this->entries = $entries;
    }
}

final class Inventory{
    
    public int $size;
    public Node $slots_tree;
    
    public function __construct(int $size){
        $this->size = $size;
        $this->slots_tree = Node::buildTree($this->size);
    }
    
    private function getNode(int $slot) : Node{
        $node = $this->slots_tree;
        $size = $this->size;
        for($i = $this->size / 2; $i >= 2; $i /= 2){
            $node = $node->entries[($slot & $i) > 0 ? 1 : 0];
        }
        return $node;
    }
    
    public function get(int $slot){
        return $this->getNode($slot)->entries[$slot & 1];
    }
    
    public function set(int $slot, $value) : void{
        $this->getNode($slot)->entries[$slot & 1] = $value;
    }
}

$inventory = new Inventory(64);
var_dump($inventory->get(55));