Send a request to call a function from another server

Send a request to call a function from another server

I have client code in php and two servers e.g apache and tomcat. I want to
call a method in tomcat server through apache. Whereas apache is running
in 81 port and tomcat is running in 85 port. the function which should be
called is in javascript(in tomcat) . what is the php code to do this?
Am new to this please help me with explanation.