PHP and MySQL® 24-Hour Trainer

Lesson 10

Reusing Code with Functions

Writing code can be time-consuming and error prone. After you have written a piece of code that works well, you want to reuse that code instead of constantly rewriting it when you need to do the same thing again.

You could copy and paste that piece of code everywhere you need it, but then if you found a new bug or thought of an enhancement, you'd need to change it everywhere that you copied it—assuming you could find all the places.

PHP lets you take those pieces of code and create mini-programs called functions out of them. Functions make it easier to read your code because functions move extraneous detail out of the main flow of the program. You learned several PHP functions in Lesson 4, such as the function strlen() that counts the number of characters:

<?php
$myName = ‘Andy’;
echo strlen($myName);

You give strlen() some information (optionally), it does something, and it (optionally) gives you something back. When it gives something back, it is said to return something.

In this lesson you learn how to take the valuable pieces of code that you've written and turn them into user functions of your own. You learn how to define the function, how to pass data to the functions, and how to get data back from the functions. Then you take that knowledge to learn how to use the functions in your code.

Another way of reusing code is include statements. You are using a simple include in the Case Study. In this lesson you also learn about the different ...