Just read this article about running PHP applications on Phalanger and found it greatly interesting that PHP apps are often quite a bit faster running on Phalanger than on the Zend engine. In fact the article states that phpBB serves up pages twice as fast from Phalanger than from Zend.
Also interesting is the existence of a managed MySQL extension for Phalanger. This appears to be based on libmysql however.
Phalanger works great on .NET but also works on Mono. This makes it very easy to use C# (or any other CLR language) to write some layers of your app, like data access code, while allowing you to write the UI in PHP. With Phalanger you use the full range of managed components like Connector/Net, LinQ, generics, custom attributes, events, and others.