A legacy application. It still earns the money, but maintaining the old code base is getting harder and harder. Feature development is too slow and the bug tracker is full of severe defect reports. Rewriting the whole application is something your developers would simply love to do. But the rewrite probably won't go live before it's running out of budget. Let's have a look at simple techniques that allow us to transform our legacy application step by step into a modern Symfony application.