Phalanger is a new PHP implementation introducing the PHP language into the family of compiled .NET languages. It provides PHP applications an execution environment that is fast and extremely compatible with the vast array of existing PHP code. Phalanger gives web-application developers the ability to benefit from both the ease-of-use and effectiveness of the PHP language and the power and richness of the .NET platform taking profit from the best from both sides.

Phalanger maintains the way how PHP web applications are developed and deployed so that the you can leverage from .NET without having to learn complex ASP.NET style of web development, however Phalanger also allows you to use PHP as a language for writing ASP.NET applications, so you have the freedom to make a choice!

Due to the managed implementation of the PHP functions library, the migration from PHP interpreter to Phalanger is an easy and straightforward process, which includes only configuring the application in most of the situations. The compiled nature of Phalanger applications also leads to major performance boost.

To get an idea on how the interoperability of PHP and C# works, head over to one of the tutorials on their site: Using PHP library from C#

Links:
Download Phlanger
Phlanger Documentation
Tutorials