PHP Class Instance into MySQL database
===

I'm working on a website in which I would like to use PHP and MySQL.
Mostly I insert hundreds of variables into my MySQL database but I am getting tired of this.
I have searched the internet for a solution but without any succes.

My website uses Object Oriented PHP and I would like to insert the whole instance into the database. 
Example:

    class User
    {
         private $userID;
         private $username;
         // etc

         public function __construct($userID, $username)
         {
               $this->userID = $userID;
               $this->username = $username
         }

         // Other functions go here
    }

I would like to know if I could save a whole instance ($user = new User($x, $y)) into my MySQL database. If possible, what field type do I need?

Thanks in advance.