Missing session support in php5
 

Please help, I have a problem with my php5/apache2 installation on Debian Sarge. I don't seem to have session support. I get:
"Fatal error: Call to undefined function session_name() in..." when loading a page containing the session_name() function.

If I had session support I guess it would be visible in phpinfo, but it's not.
Session support are supposed to be enabled in php by default. But I think you can compile without it if you want. I didn't do anything like that, I just installed packages like this:
# apt-get install php5 libapache2-mod-php5 php5-curl php5-gd

So what do I need to do? Activate any module/extension (how)? Or get the source and recompile?
I tried this but it didn't work:
# php5.0-modconf apache2 enable session

Any help appreciated, this is just too weird for me :confused:

Here is my phpinfo
http://www.magnus.ws/phpinfo-copy.htm