Best way for check user is logged in or not

[eluser]mTuran[/eluser]
Thanks for replying but i don't wanna use ready library because i coded my user model file(i didn't coded library, it is library) The model file called USER can create new user, sign method or reset password method etc...

Now i confused about remember me function. I coded remember me function if user select remember me when loging in system create cookie for identity user at next visit. but i have to auto load any function which is check cookie and do auto login in every pages.