The manual says: "If 'URL fopen wrappers' are enabled in PHP (which they are in the default configuration), you can specify the file to be include()ed using an URL instead of a local pathname. See Remote files and fopen() for more information."
So, if the remote server supports HTTP:
include ("http://192.58.0.23/MyServlet");
... is legal. However, if the remote server parses and executes PHP code, and you are attempting to include that code for local execution, the results will not be what you desire.