Simple question - how to make user login?

[typo27]

Privet,
Does anybody knows how to make user login (having username) to the system.
I know only one way - to make the form with fields: user, pass, logintype and maybe pid, submit the form (via JS) and let the system itself to login the user.
But what if I want to login user myself?
What function to use for that purpose?
Lets say in cakePHP in order to login user it is enough to set one or two session variables $_$SESSION['user']='John' and user is considered logged in.

The way with submitting the form by JS is not suitable for me for 2 reasons:
1. Javascript may be switched off on user browser.
2. Using kbmd5fepw extension for superchallenging passwords makes the problem completely insane.

Sposibo