Is it possible to integrate Zend Framework with already existing legacy web application? The application is written horribly using so called spaghetti code (no separation between presentation and application logic, PHP, HTML and SQL are all together). It is a very large application with hundreds of pages and forms.
Does it make sense to introduce a framework now or should we just continue with the spaghetti code? It is not realistic to rewrite the whole application using a framework because it would be too difficult. Moreover, we need to add some new functionality to the application and we have a deadline. Should we use a framework for all the new parts of the website that we need to add or should we just go with the way it has been programmed by developers that worked on it before us?
I think you really could and should code the new bits of your application using a framework, and migrate the legacy bits to it whenever they bug. Refactoring is not difficult and can be done over a long period of time, and that could be a task when you feel bored.
I advise you to read this very interesting article about refactoring : http://www.joelonsoftware.com/articles/fog0000000348.html , by Joël Spolsky