I need to convert a single line of code from .NET to PHP. I'm hoping that there is a .NET developer here that also knows PHP. Since I don't know .NET, I'm not even sure where I can find relevant documentation.

Code:
string newString = Convert.ToBase64String(SHA512.Create().ComputeHash(Encoding.ASCII.GetBytes(oldString)));
Thanks in advance for any help that you can provide...