CI Upgrade from 2.2.1 to 3.1.5

I am working on CI upgradation for my site from 2.2.1 to 3.1.5.
I followed the manual for same and did step by step.
But still nothing works.
Before upgradation my site was working properly.
Please let me know if anybody have any idea about this kind of issues

Thanks in Advance!

i migrated 3 projects from CI 2.x to 3.1.5 successfully, just follows the rule as per guide. All class file name starts with Upper case for first letter (applied for controllers/ models/ libraries). I was spending most time for changing filename and few others changes in config so on but nothing really major.

One thing I did notice that only the filename needed with uppercase for its first letter. On the actual class you may not need to do so such as

my previous class such as example.php to Example.php and my actual class content was like

class example extends CI_Controller{
//etc
}

I didnt change it to class Example and it still works

Good luck

You need to upgrade each version none stop.

What did you Try? What did you Get? What did you Expect?

Joined CodeIgniter Community 2009.  ( Skype: insitfx )

I also migrated a few sites and had no problems.
But be very precice to follow the manual.

On the package it said needs Windows 7 or better. So I installed Linux.

Thank you for your replies!

I did follow the manual step by stem, but still its not working.
The problem which I have found is that in CodeIgniter.php , for $RTR object , class file is not found.

$e404 = FALSE;
$class = ucfirst($RTR->class);
$method = $RTR->method;
if (empty($class) OR ! file_exists(APPPATH.'controllers/'.$RTR->directory.$class.'.php'))

here the $class variable is always blank, it has to be something wrong with routing but I am unable to understand.
Any help would really be really great!