Notice: session_start(): ps_files_cleanup_dir: opendir(/var/lib/php5) failed: Permission denied (13)

When trying to start a new session in PHP on your Ubuntu web server, like this:

session_start();

Then you sometimes might get this:

Notice: session_start(): ps_files_cleanup_dir: opendir(/var/lib/php5) failed: Permission denied (13) in /home/steffe/public_html/fb2_log.php on line 185

The most easy way to solve this problem is very straight forward but quite ugly. By prepending @ to the function call, the function will never print out the error:

@session_start();

This will simply hide the error message, and I believe that this is what most people want.

If one looks deeper into the problem, one will find that there are permission conflicts between some packages in the server. There are more correct ways of solving this problem, but this was enough for me!