Medusa\Tree\PersistentAvlTree::add PHP Method

    public function add($key, $value)
    {
        $c = $this->compare($this->key, $key);
        if ($c === 0) {
            return new self($key, $value, $this->left, $this->right);
        } else {
            if ($c > 0) {
                return $this->makeBalanced(new self($this->key, $this->value, $this->left, $this->right->add($key, $value)));
            } else {
                return $this->makeBalanced(new self($this->key, $this->value, $this->left->add($key, $value), $this->right));
            }
        }
    }