Need to convert 1 C# IHttpHandler page into a PHP page, the total code involve is
120 lines main handler
350 lines utility class use by the handler
The code involve use of the .NET [login to view URL] classes
The code retrieve XML from external URL and use the data in the XML to validate incoming request.
Request are encrypted and need to be decrypted and answer need to be encrypted.
Attached the C# source code