The official silverlight website is at http://silverlight.net/ and in case your wondering, silverlight was originally developed in aspx or asp.net. (Microsofts server-side language.) But as for redeveloping it in php, I would suggest using a lot of css templates and maybe even copy some of the silverlight css code if it isn't too messy.

I came across a write up in which the author was calling an include PHP file which has extension ".PHPX"

The argument is they are writing silver light applications in PHP.

May be someone needs to read this link.

http://tomasp.net/blog/php-in-silverlight.aspx