lithium\storage\session\adapter\Php::delete PHP Method

    public function delete($key, array $options = array())
    {
        if (!$this->isStarted() && !$this->_start()) {
            throw new RuntimeException('Could not start session.');
        }
        $self = $this;
        return function ($class, $params) use($self) {
            $key = $params['key'];
            $self->overwrite($_SESSION, Set::remove($_SESSION, $key));
            return !Set::check($_SESSION, $key);
        };
    }