I want to upgrade my cakephp application from 2.3.4 to latest version . I am not getting required information from official website . Can any one tell me the step by step of the process ?
Thanks in advance.
CakePHP 2.x to 3.0 is a huge update which may require a lot of manual work, you should check  and especially . After you have upgraded to the latest Cake 3  the update to Cake 4  (“latest version”) is comparably trivial.
So in short there are tools to help you in the transition, but there isn’t an “just do these three easy steps” approach. Depending on how complex your project is you have to refactor a lot.
For that big upgrade I would just start a new application and migrate your code over.
Yes it will take a little time but probably will be worth it.