codeigniter session to third party site

[eluser]xeroblast[/eluser]
hi,

i need your help on how to take the codeigniter sessions to be use as post data in another site such as phpbb or wordpress or joomla which are put in the iframe.

this is what i had in mind, the main site, which is codeigniter, where the user login its username and password. and this username and password is the same with the third party site like the phpbb or wordpress or joomla. so when user logins in codeigniter, the user is also automatically login to these sites using the username and password in the codeigniter.

i have a simple idea using the jquery post [$.post('3rdparty/login.php', post-data-here)] but i must work on the codeigniter controller which i have no idea on how to do it.

thanks for the help in advance.