Unable to call com registered dll function in php

I have completed the com registration of a dll file and it is showing in the registry(which I got after entering regedit in command prompt)
If I use $obj1 = new COM("Encryptiondll.ClsEncryption"); I am getting no error
But when I am trying to access a method(which is declared as public string in .net) I am getting the following error from my php code
Fatal error: Call to undefined method com::Encrypt12() in C:\xampp\htdocs\test1\index.php on line 12
Please help