PHP Introduction

What is PHP?

PHP is Hypertext Pre-processor is a server-side scripting language designed for Web development. It was originally created by Rasmus Lerdorf in 1994; the PHP reference implementation is now produced by The PHP Group. PHP is a widely-used open source general-purpose scripting language that is especially suited for web development and can be embedded into HTML.

Example # An introductory example

<!DOCTYPE HTML>

<html>

<head>

<title>Example</title>

</head>

<body>

<?php

echo “Hi, I’m a PHP script!”;

?>

</body>

</html>

 

Instead of lots of commands to output HTML (as seen in C or Perl), PHP pages contain HTML with embedded code that does “something” (in this case, output “Hi, I’m a PHP script!”). The PHP code is enclosed in special start and end processing instructions that allow you to jump into and out of “PHP mode.”

PHP History

PHP as it’s known today is actually the successor to a product named PHP/FI. Created in 1994 by Rasmus Lerdorf, the very first incarnation of PHP was a simple set of Common Gateway Interface (CGI) binaries written in the C programming language. Originally used for tracking visits to his online resume, he named the suite of scripts “Personal Home Page Tools,” more frequently referenced as “PHP Tools.” Over time, more functionality was desired, and Rasmus rewrote PHP Tools, producing a much larger and richer implementation. This new model was capable of database interaction and more, providing a framework upon which users could develop simple dynamic web applications such as guestbooks. In June of 1995, Rasmus » released the source code for PHP Tools to the public, which allowed developers to use it as they saw fit. This also permitted – and encouraged – users to provide fixes for bugs in the code, and to generally improve upon it.

Example # Example PHP/FI Code

 

<!–include /text/header.html–>

<!–getenv HTTP_USER_AGENT–>

<!–ifsubstr $exec_result Mozilla–>

Hey, you are using Netscape!<p>

<!–endif–>

<!–sql database select * from table where user=’$username’–>

<!–ifless $numentries 1–>

Sorry, that record does not exist<p>

<!–endif exit–>

Welcome <!–$user–>!<p>

You have <!–$index:0–> credits left in your account.<p>

<!–include /text/footer.html–>

 

PHP 3

PHP 3.0 was the first version that closely resembles PHP as it exists today. Finding PHP/FI 2.0 still inefficient and lacking features they needed to power an eCommerce application they were developing for a university project, Andi Gutmans and Zeev Suraski of Tel Aviv, Israel, began yet another complete rewrite of the underlying parser in 1997. Approaching Rasmus online, they discussed various aspects of the current implementation and their redevelopment of PHP. In an effort to improve the engine and start building upon PHP/FI’s existing user base, Andi, Rasmus, and Zeev decided to collaborate in the development of a new, independent programming language. This entirely new language was released under a new name, that removed the implication of limited personal use that the PHP/FI 2.0 name held. It was renamed simply ‘PHP’, with the meaning becoming a recursive acronym – PHP: Hypertext Preprocessor.

PHP 4

By the winter of 1998, shortly after PHP 3.0 was officially released, Andi Gutmans and Zeev Suraski had begun working on a rewrite of PHP’s core. The design goals were to improve performance of complex applications, and improve the modularity of PHP’s code base. Such applications were made possible by PHP 3.0’s new features and support for a wide variety of third party databases and APIs, but PHP 3.0 was not designed to handle such complex applications efficiently.

PHP 5

PHP 5 was released in July 2004 after long development and several pre-releases. It is mainly driven by its core, the Zend Engine 2.0 with a new object model and dozens of other new features.

PHP’s development team includes dozens of developers, as well as dozens others working on PHP-related and supporting projects, such as PEAR, PECL, and documentation, and an underlying network infrastructure of well over one-hundred individual web servers on six of the seven continents of the world. Though only an estimate based upon statistics from previous years, it is safe to presume PHP is now installed on tens or even perhaps hundreds of millions of domains around the world.

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