The company I work for is going in the opposite direction. I'll be expected to learn PHP soon after spending years developing with .NET. I'd much prefer to be switching to Ruby or Python. Anyway if you want to switch to Ruby on Rails in future you won't have a massive leap. ASP.NET MVC is very similar.
Man that is weird. As a .NET developer I recently volunteered to maintain a PHP site for a not for profit museum. The site was written by a local web dev company, so without knowing better I assume it was built at least somewhat professionally.
It took me a few weeks to get the hang of it, working a few hours each evening. I enjoyed the process but now that I understand how it hangs together I fail to see the appeal. It is a fairly simple environment, without much depth or breadth. I now understand why the PHP job ads I see seem to pay a lot less than .NET jobs.
That said, after 11 very good years of Microsoft .NET development, I'm going 100% non-Microsoft for my personal project that I hope to turn into a paying product. After the Windows 8 fiasco and the carnage of the internal Microsoft politics that caused it, I believe Microsoft lost their ability to take good care of developers. But a useful side effect is that they created a giant escape hatch with WinJS apps.
