Login to DA

I have a reseller DirectAdmin panel and I want to make a script which be accessible after user authorization to DA and vice versa.

Íîw can I do a login-form to the DA from my own site?
How does DA control user-sessions?

This might help:
http://help.directadmin.com/item.php?id=61

jmstacey said:

This might help:
http://help.directadmin.com/item.php?id=61

Click to expand...

Thx. its very useful for me.
But How can I control user-session in my script?