Issue with overriding core functionality in magento

I'm aware of the override principal in Magento, where I should create a copy of the file and tree from "core" into "local" of the file I want to override.

I have 2 instances of the site. 1 as development server and other live server. I have overridden a admin functionality on the development server successfully. But, when开发者_C百科 I wanted to implement this on live server in same fashion. This doesn't work.

Only difference on live site is "cashing" on. I refreshed and flushed the caching on live and checked many times the files and path all are correct. But still functionality is not working.

Can anyone please suggest the way or possible reason why this is not working on live server.

There could be many reasons why it is not working on the live server.

Is your production server and live server have everything same i.e. same OS, same mysql, php version. Is the live server setup the same way as your production server with same php, mysql and apache configuration etc etc...