PHP and MySQL Web Development 4th Ed-tqw-_darksiderg

5
Reusing Code and Writing
Functions
THIS CHAPTER EXPLAINS HOW REUSING CODE leads to more consistent, reliable, maintainable
code, with less effort.We demonstrate techniques for modularizing and reusing
code, beginning with the simple use of require() and include() to use the same code
on more than one page.We explain why these includes are superior to server-side
includes.The example given here covers using include files to get a consistent look and
feel across your site.We also explain how you can write and call your own functions
using page and form generation functions as examples.
Key topics covered in this chapter include
n The advantages of reusing code
n Using require() and include()
n Introducing functions
n Defining functions
n Using parameters
n Understanding scope
n Returning values
n Calling by reference versus calling by value
n Implementing recursion
n Using namespaces
The Advantages of Reusing Code
One of the goals of software engineers is to reuse code in lieu of writing new code.
The reason for this is not that software engineers are a particularly lazy group. Reusing
existing code reduces costs, increases reliability, and improves consistency. Ideally, a new
project is created by combining existing reusable components, with a minimum of
development from scratch.