Basic PHP – Part 1


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What is PHP?

PHP (officially “PHP: Hypertext Preprocessor”;) is a server-side HTML-embedded scripting language.

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

Example 1-1. An introductory example

<html>

<head>

<title>Example</title>

</head>

<body>

<?php

echo “Hi, I’m a PHP script!”;

?>

</body>

</html>

Notice how this is different from a CGI 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 a 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.

What can PHP do?

At the most basic level, PHP can do anything any other CGI program can do, such as collect form data, generate dynamic page content, or send and receive cookies.

Perhaps the strongest and most significant feature in PHP is its support for a wide range of databases. Writing a database-enabled web page is incredibly simple. The following databases are currently supported:

Adabas D Ingres Oracle (OCI7 and OCI8)
dBase InterBase Ovrimos
Empress FrontBase PostgreSQL
FilePro (read-only) mSQL Solid
Hyperwave Direct MS-SQL Sybase
IBM DB2 MySQL Velocis
Informix ODBC Unix dbm

PHP also has support for talking to other services using protocols such as IMAP, SNMP, NNTP, POP3, HTTP and countless others. You can also open raw network sockets and interact using other protocols.

A brief history of PHP

PHP was conceived sometime in the fall of 1994 by Rasmus Lerdorf. Early non-released versions were used on his home page to keep track of who was looking at his online resume. The first version used by others was available sometime in early 1995 and was known as the Personal Home Page Tools. It consisted of a very simplistic parser engine that only understood a few special macros and a number of utilities that were in common use on home pages back then. A guestbook, a counter and some other stuff. The parser was rewritten in mid-1995 and named PHP/FI Version 2. The FI came from another package Rasmus had written which interpreted html form data. He combined the Personal Home Page tools scripts with the Form Interpreter and added mSQL support and PHP/FI was born. PHP/FI grew at an amazing pace and people started contributing code to it.

It is difficult to give any hard statistics, but it is estimated that by late 1996 PHP/FI was in use on at least 15,000 web sites around the world. By mid-1997 this number had grown to over 50,000. Mid-1997 also saw a change in the development of PHP. It changed from being Rasmus’ own pet project that a handful of people had contributed to, to being a much more organized team effort. The parser was rewritten from scratch by Zeev Suraski and Andi Gutmans and this new parser formed the basis for PHP Version 3. A lot of the utility code from PHP/FI was ported over to PHP 3 and a lot of it was completely rewritten.

The latest version (PHP 4) uses the Zend scripting engine to deliver higher performance, supports an even wider array of third-party libraries and extensions, and runs as a native server module with all of the popular web servers.

Today (1/2001) PHP 3 or PHP 4 now ships with a number of commercial products such as Red Hat’s Stronghold web server. A conservative estimate based on an extrapolation from numbers provided by Netcraft (see also Netcraft Web Server Survey) would be that PHP is in use on over 5,100,000 sites around the world. To put that in perspective, that is slightly more sites than run Microsoft’s IIS server on the Internet (5.03 million).

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