Programming PHP

Chapter 13 CHAPTER 13
Application Techniques
By now, you should have a solid understanding of the details of the PHP language and
its use in a variety of common situations. Now we’re going to show you some techniques
that you may find useful in your PHP applications, such as code libraries, templating
systems, efficient output handling, error handling, and performance tuning.
Code Libraries
As you’ve seen, PHP ships with numerous extension libraries that combine useful
functionality into distinct packages that you can access from your scripts. In previous
chapters, we’ve covered using the GD, pdflib, and Sablotron extension libraries,
and Appendix B lists all of the available extensions.
In addition to using the extensions that ship with PHP, you can create libraries of
your own code that you can use in more than one part of your web site. The general
technique is to store a collection of related functions in a file, typically with a .inc file
extension. Then, when you need to use that functionality in a page, you can use
require_once( ) to insert the contents of the file into your current script.
For example, say you have a collection of functions that help create HTML form elements
in valid HTML—one function creates a text field or a textarea (depending on
how many characters you tell it the maximum is), another creates a series of pop-ups
from which to set a date and time, and so on. Rather than copying the code into
many pages, which is tedious, error-prone, and makes it difficult to fix any bugs
found in the functions, creating a function library is the sensible choice.
When you are combining functions into a code library, you should be careful to
maintain a balance between grouping related functions and including functions that
are not often used. When you include a code library in a page, all of the functions in
that library are parsed, whether you use them all or not. PHP’s parser is quick, but
not parsing a function is even faster. At the same time, you don’t want to split your
functions over too many libraries, so that you have to include lots of files in each
page, because file access is slow.
This is the Title of the Book, eMatter Edition
Copyright © 2002 O’Reilly & Associates, Inc. All rights reserved.
297