While using PHP’s session_start function, an error started showing as:

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

Here’s a simple solution.

Solution – Notice: session_start(): ps_files_cleanup_dir: opendir failed: Permission denied

To resolve this error, all you need to do is to open up your php.ini file, which is usually existing in the following path:
/etc/php5/apache2

and change the value of variable session.gc_probability to 0, if the value is 1, or if the value is 1 then change it to 0.

Now restart the apache server through the following command as in linux terminal:
sudo /etc/init.d/apache2 restart

and the error could have been resolved.