Ethernet controlled LED HELP?

Ethernet controlled LED HELP?

I want to control a 5v relay

Make up your mind...

How could I control a relay from a php webserver?

php is a scripting language, not a web server. Apache is a web server.

A server provides data. A client connects to the server to get the data. When it connects, it specifies some script on the host machine to be executed. That can be a php script.

What, exactly, is this php script doing to define the relay/LED state?