this is really cool. I observed the Phalanger project quite some time now. They implemented PHP on .net .
I now heard that the team showed a demo using PHP on .net within Silverlight. You can try it yourself here http://php-compiler.net/doku.php?id=php-in-silverlight
Hey, how it starts to pay off. When .net started Java was the theme of the time. Java's promise was one language, any platform. Ever since the Java community struggles with this promise and I remember seeing the book of one J2EE vendor talking how to "migrate" from a different J2EE platform to their own. The book was extremely thick.... anyway.
.net started with a different approach. While still having the notion of a runtime to abstract certain aspects of the hardware or operation systems underneath. But - and this were the two new aspects of .net - it never claimed to make all platforms just the same (think about Compact Framework which has the .net baseline but is different in things that are different) and it came with the notion of supporting "any" programming language (as long as it supports some ideas).
Now the any language part is getting really interesting. Today there is a bandwidth of languages available. It started with languages that differentiates only in syntactical specifics (compare VB.NET and C# in the first generation). Now today the traditional languages differentiates on their specifics (C# is more "academic", using more constructs which are known from dynamic languages while VB.NET is heading more in the tradition of VB, simplicity and fast results). Today functional programming and even dynamic languages are part of the game.
Don't get me wrong: Java is heading somehow in same directions (JRuby etc.). But I think still the two basic distinctions still remain.