Default controller not working

One of my codeigniter application(version2.2) was working fine in the XAMPP(php version 5.5).
Now i updated my XAMMP with php version 5.6- this case my controller stops the functioning.

below is my configuration in autoload.php
now  $autoload["libraries"]=array('database','session')

if i remove database in the above array, controller start functioning properly. But without database i cant do anything in the application

Please help me.