php manual PHP Manual - introduction

PHP, short for "PHP: Hypertext Preprocessor", is an open-source, reflective programming language used mainly for developing server-side applications and dynamic web content, and more recently, other software.

PHP allows interaction with a large number of relational database management systems, such as MySQL, Oracle, IBM DB2, Microsoft SQL Server, PostgreSQL and SQLite. PHP runs on most major operating systems, including UNIX, Linux, Windows, and Mac OS X, and can interact with many major web servers. The official PHP website contains extensive documentation.

There is a command line interface, as well as GUI libraries such as the Gimp Tool Kit (GTK+) and text mode libraries like Ncurses and Newt.

PHP is the result of the efforts of many contributors. It is licensed under the PHP License, a BSD-style license. Since version 4, it has been powered by the Zend engine.

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Chapter 1. Introduction

What is PHP?

PHP (recursive acronym for "PHP: Hypertext Preprocessor") is a widely-used Open Source general-purpose scripting language that is especially suited for Web development and can be embedded into HTML.

Simple answer, but what does that mean? An example:

Example 1-1. An introductory example


echo "Hi, I'm a PHP script!";


Notice how this is different from a script written in other languages like Perl or C -- instead of writing a program with lots of commands to output HTML, you write an HTML script with some embedded code to do something (in this case, output some text). The PHP code is enclosed in special start and end tags that allow you to jump into and out of "PHP mode".

What distinguishes PHP from something like client-side JavaScript is that the code is executed on the server. If you were to have a script similar to the above on your server, the client would receive the results of running that script, with no way of determining what the underlying code may be. You can even configure your web server to process all your HTML files with PHP, and then there's really no way that users can tell what you have up your sleeve.

The best things in using PHP are that it is extremely simple for a newcomer, but offers many advanced features for a professional programmer. Don't be afraid reading the long list of PHP's features. You can jump in, in a short time, and start writing simple scripts in a few hours.

Although PHP's development is focused on server-side scripting, you can do much more with it. Read on, and see more in the What can PHP do? section, or go right to the introductory tutorial if you are only interested in web programming.