I have a client that wants to develop his web applciation using "Open Source". Now the term is open to a wide variety of interpretations. Some might even argue that ASP.NET is open source, since you can use Visual Web Developer to develop it with, which is free. Also, using mySQL as opposed to SQL Server is an open source scenario.

My gut tells me to fear developing his app in PHP more than a fortnight in hell. This is because it is a very large, ambitious and extremely data-driven project. My feeling is that by using ASP.NET 2.0 with Visual Studio 2005, we can dramatically reduce the necessary code, make it infinitely more scaleable and maintainable, plus create a much more enjoyable development experience (my #1 goal).

Now the project is likely to have a pretty substantial development budget, so you could always do it in PHP with more code, written by more developers getting paid less. This is exactly what my worst nightmare is. It seems like fewer developers using a better set of collaborative tools is the way to go. Just having .NET's object model, and design-time environment is a huge benefit, but user-controls, master pages...I know I'm preaching to the choir.

What I need now is some evidence to support my position. Can any of you folks share your experiences that my illustrate my point? Better yet, does anyone know of any good articles, or independent studies/surveys on the subject of ASP.NET 2.0 vs. PHP? That would be a big help.

Thank you.

Aaron