Is there any guidance on how best to upgrade an app to 2.0.49?

Some years ago I wrote a program; its current edition is Yii 2.0.35 and PHP 7.4. I have been asked to update this to run on 2.0.49 and PHP 8.3. Updating Yii and PHP is no problem - but I am worried about the work involved in updating the app. For example I see that bootstrap 5 seems quite different from Bootstrap 3 and the thought of all that editing… This kind of problem must be common, so is there some wise advice out there on how best to tackle this issue? I would be very grateful if you could save me from making a total mess!

PS One idea would be to run yii 2.0.49 using Bootstrap 3 (and jQuery) instead of the default Bootstrap5. Would that be inadvisable?

  1. Don’t update everything at once if possible.
  2. If you have automated tests, you’re super-lucky.
  3. Check GitHub - rectorphp/rector: Instant Upgrades and Automated Refactoring of any PHP 5.3+ code

Yes. We have a BS3 app running on latest Yii on PHP8.3
Unless you rely on some 3rd part extensions, it should’t be hard.