Advice on upgrade legacy app from 1.7.0?

Hi all,

I have inherited an old application created on CI 1.7.0 which I have been able to get running on PHP 7.1.18.
(It hits a fatal error on PHP 7.2.6!)

Ideally I would like to upgrade it to CI 3.x and I am seeking some general ideas on the best way forward.

My original plan was to incrementally upgrade the existing application through the releases but I am not 100% sure what code is CI framework and what code is application so overlaying the release tends to wipe out the application.

Would you advise trying from the other end? That is, install the latest 3.x with PHP 7.2.6 and attempt to port the application code to that?

I have a lot to learn so will welcome any advice you might share.

Thank you,
 - jon

Depending how big the application are I would just re-write it from scratch.
If not; use the upgrade guides. Have used them a couple of times (from 2 not 1 thought).

Simple start aw new app

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

Joined CodeIgniter Community 2009.  ( Skype: insitfx )

Thanks all.
Right now, I don't have the skills to re-write it.
However, (just in case anyone comes across this thread in the future)
on closer inspection, my legacy app appears to have CI code from several versions: 1.7.0, 1.7.2, 2.2.0 and 2.2.6 at least!
Therefore, I have installed a fresh CI 2.2.6 and compared my app tree to this version. Then I have ported across missing files and updated configuration to give a relatively consistent version.
At this time it is mostly working and, at least, a better position to start.

There have been changes to both the ./application and ./system folders since version 1.7.0

So you cannot just copy some files over.

you need to copy the ./system folder on every new update but if changes were made to
the ./application folder then those files will also need to be copied over.

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

Joined CodeIgniter Community 2009.  ( Skype: insitfx )