Also, as you have different lessons, its important to teach good styling.
PHP Code:
function onCreated() {
echo("Hello World!");
}
is much better than
PHP Code:
function onCreated(){echo("Hellow World!");}
Or any other variation, as people like to do weird stuff while styling...
It just makes it easier for others to read your code.
Also, indenting the script inside a function/brackets makes it much easier to read than if everything is indented the same. :P