src/Http/Session.php
public function get($key = null)
    {
        return (is_null($key) ? $_SESSION : ($this->has($key) ? $_SESSION[$key] : null));
    }
public function get($key = null)
    {
        return (is_null($key) ? $_SESSION : ($this->has($key) ? $_SESSION[$key] : null));
    }
Get session method.

@param string $key

@return null|mixed