Chapter 1. Introduction to PHP Contents:
What Does PHP Do?
A Brief History of PHP
Installing PHP
A Walk Through PHP
PHP is a simple yet powerful language designed for creating HTML content. This chapter covers
essential background on the PHP language. It describes the nature and history of PHP; which
platforms it runs on; and how to download, install, and configure it. This chapter ends by showing
you PHP in action, with a quick walkthrough of several PHP programs that illustrate common
tasks, such as processing form data, interacting with a database, and creating graphics.
1.1. What Does PHP Do?
PHP can be used in three primary ways:
Server-side scriptingPHP was originally designed to create dynamic web content, and it is still best suited for
that task. To generate HTML, you need the PHP parser and a web server to send the
documents. Lately, PHP has also become popular for generating XML documents, graphics,
Flash animations, PDF files, and more.
Command-line scripting
PHP can run scripts from the command line, much like Perl, awk, or the Unix shell. You
might use the command-line scripts for system administration tasks, such as backup and
log parsing.
Client-side GUI applications
Using PHP-GTK (http://gtk.php.net), you can write full-blown, cross-platform GUI
applications in PHP.
In thi
s book, we'll concentrate on the first item, using PHP to develop dynamic web content.
PHP runs on all major operating systems, from Unix variants including Linux, FreeBSD, and
Solaris to such diverse platforms as Windows and Mac OS X. It can be used with all leading web
servers, including Apache, Microsoft IIS, and the Netscape/iPlanet servers.
The language is very flexible. For example, you aren't limited to outputting just HTML or other
text files—any document format can be generated. PHP has built-in support for generating PDF
files, GIF, JPG, and PNG images, and Flash movies.
One of PHP's most significant features is its wide-ranging support for databases. PHP supports
all major databases (including MySQL, PostgreSQL, Oracle, Sybase, and ODBC-compliant
databases), and even many obscure ones. With PHP, creating web pages with dynamic content
from a database is remarkably simple.
Finally, PHP provides a library of PHP code to perform common tasks, such as database
abstraction, error handling, and so on, with the PHP Extension and Application Repository
(PEAR). PEAR is a framework and distribution system for reusable PHP components. You can
find out more about it at http://pear.php.net.
