The first call to the addHeader method demonstrates the point

To use the class, we've instantiated it with the new keyword. The object created

from the class is placed in the $webPage variable. Through this variable, we have

access to all the members of the object as we did with the $this variable above.

The first call to the addHeader method demonstrates the point:

$webPage->addHeader('A Page Built with an Object');

Only at the end, upon calling the get method, do we actually get anything back

from the class. No longer do we need to worry about passing around a variable

that contains the contents of the page—the class takes care of that.

Avoid output in classes

Instead of get, we could have endowed the Page class with a method called

write to send the page code to the browser immediately. This would have

made the code above slightly simpler, as the main script would not have had

to get the code from the object and echo it itself. We avoided this for a

reason.

It's usually a bad idea to output directly from inside a class (with statements

and functions such as echo and printf); doing so will reduce the flexibility

of your classes. Allowing the value to be retrieved from the class gives you

the option of performing additional transformations on it before you send

it to the browser, or use it for some other purpose entirely (like putting it in

an email!).

Notice also that the number of lines of code we have to write to use the class is

fewer than were required in the earlier examples. Although it's impossible to determine

good application design by counting the number of lines of code, it is

clear that the class has made the procedural code that uses it much simpler. From

the point of view of people reading the code, it's already fairly clear what's going

on, even without them having to look at the code for the Page class.