src/core/Session.php
public function destroyWithCookie(): ?bool
    {
        if ($this->isStarted()) {
            $this->destroy();
            return setcookie($this->getName(), '', time() - 1, '/');
        }
        return null;
    }
public function destroyWithCookie(): ?bool
    {
        if ($this->isStarted()) {
            $this->destroy();
            return setcookie($this->getName(), '', time() - 1, '/');
        }
        return null;
    }
It complitly destroys session with cookie.
@return boolean|null The result.