<?php
// First we're going to *define* the say_hello() function
function say_hello() {
echo 'Hello world!'; // This is what the function will do when called
}
// Now we're going to *call* the say_hello() function
say_hello(); // This will print "Hello world!" into the HTML document
// Uh oh! We're calling a function that isn't defined. We'll get a fatal error if we do this.
say_something_else();
?>