I am working in IT department of a big, international company. We are developing different Intranet applications for the business (Complaints, Rebates, Service Desk etc). Now we decided to migrate from PHP platform to .NET (integration with MS CRM Dynamics, Exchange and MS Office be among many reasons). As there are about 20 different applications the business is using on current, PHP platform, we will have to come up with the best way to move them all to the new platform. I don't want to go into details how to convert the code etc, as while we do migrate we want to improve all of these applications.
So we came up with 2 main ways of moving these apps:
Support just one platform. What would it mean? Create homepage and literally migrate all apps as they are to .NET (without improving them while we do that). After New intranet is running we would start rebuilding migrated applications and improving them. That would save us developing intranet in .NET while having to support PHP platform.
Support both platforms for some time. That would mean building just a homepage and 1 or 2 new applications (which do not exist on our PHP platform). Making these available to the users but not taking off the PHP platform (we would incorporate menus and links to make it easier for users to move between apps on PHP page and the new one). Then we would start rewriting the PHP applications while improving them.
Now I am not sure what would be better, on one hand (option 1) we will potentially make everything easier for users by not forcing them to use two different platforms at the same time. Although they won't see any improvement of having the new platform, apart from everything looking nicer, the functionality of applications on the new platform will be the same for some time. Also I think we would add ourselves (IT dep) more work as esentially we would write every app twice.
On the other hand in option two (2) users would have worse experience as two platforms look different, but they would realise the benefits of the new platform as new applications are beeing moved.
Has any of you came across something like that? What would you choose? Or maybe there is even different, better way to those I have presented? I would like to know what do you think and how would you approach that.