2001-08-19 11:09:18 +00:00
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<?xml encoding="iso-8859-1"?>
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2001-11-09 15:48:16 +00:00
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<!-- $Revision: 1.20 $ -->
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1999-06-06 18:51:02 +00:00
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<chapter id="introduction">
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<title>Introduction</title>
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<sect1 id="intro-whatis">
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<title>What is PHP?</title>
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<simpara>
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1999-11-15 07:51:00 +00:00
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PHP (officially "PHP: Hypertext Preprocessor") is a server-side
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HTML-embedded scripting language.
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</simpara>
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<para>
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Simple answer, but what does that mean? An example:
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</para>
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1999-06-19 21:58:55 +00:00
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<para>
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<example>
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<title>An introductory example</title>
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<programlisting role="php">
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<![CDATA[
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<html>
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<head>
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<title>Example</title>
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</head>
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<body>
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2000-08-31 05:56:42 +00:00
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<?php
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echo "Hi, I'm a PHP script!";
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?>
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2001-11-09 15:48:16 +00:00
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</body>
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</html>
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]]>
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</programlisting>
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</example>
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</para>
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1999-06-20 01:21:17 +00:00
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<para>
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Notice how this is different from a CGI script written in other
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languages like Perl or C -- instead of writing a program with lots
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of commands to output HTML, you write an HTML script with a some
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embedded code to do something (in this case, output some
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text). The PHP code is enclosed in special <link
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linkend="language.basic-syntax.phpmode">start and end tags</link>
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that allow you to jump into and out of PHP mode.
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</para>
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<para>
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What distinguishes PHP from something like client-side Javascript
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is that the code is executed on the server. If you were to have a
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script similar to the above on your server, the client would receive
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the results of running that script, with no way of determining what
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the underlying code may be. You can even configure your web server
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to process all your HTML files with PHP, and then there's really no
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way that users can tell what you have up your sleeve.
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</para>
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</sect1>
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<sect1 id="intro-whatcando">
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<title>What can PHP do?</title>
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<para>
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At the most basic level, PHP can do anything any other CGI
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program can do, such as collect form data, generate dynamic
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page content, or send and receive cookies.
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</para>
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<para>
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Perhaps the strongest and most significant feature in PHP is its
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support for a wide range of databases. Writing a database-enabled
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web page is incredibly simple. The following databases are currently
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supported:
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<blockquote>
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<simplelist columns="3">
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<member>Adabas D</member>
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<member>dBase</member>
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<member>Empress</member>
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<member>FilePro (read-only)</member>
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<member>Hyperwave</member>
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<member>IBM DB2</member>
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<member>Informix</member>
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<member>Ingres</member>
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<member>InterBase</member>
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<member>FrontBase</member>
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<member>mSQL</member>
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<member>Direct MS-SQL</member>
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<member>MySQL</member>
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<member>ODBC</member>
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<member>Oracle (OCI7 and OCI8)</member>
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<member>Ovrimos</member>
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<member>PostgreSQL</member>
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<member>Solid</member>
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<member>Sybase</member>
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<member>Velocis</member>
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<member>Unix dbm</member>
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</simplelist>
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</blockquote>
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</para>
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<para>
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PHP also has support for talking to other services using protocols
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such as IMAP, SNMP, NNTP, POP3, HTTP and countless others. You can also
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open raw network sockets and interact using other protocols.
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</para>
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2000-06-07 16:49:38 +00:00
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<!--
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<figure>
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<title>Internal Structure</title>
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<graphic fileref="../images/php3_internal_structure.gif"/>
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</figure>
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<figure>
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<title>Request Scheme</title>
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<graphic fileref="../images/php3_request_scheme.gif"/>
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</figure>
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-->
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1999-12-19 17:16:54 +00:00
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</sect1>
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<sect1 id="intro-history">
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1999-08-01 00:37:07 +00:00
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<title>A brief history of PHP</title>
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<simpara>
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PHP was conceived sometime in the fall of 1994 by &link.rasmus;.
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Early non-released versions were used on his home page to keep
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track of who was looking at his online resume. The first version
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used by others was available sometime in early 1995 and was known
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as the Personal Home Page Tools. It consisted of a very
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simplistic parser engine that only understood a few special macros
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and a number of utilities that were in common use on home pages
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back then. A guestbook, a counter and some other stuff. The
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parser was rewritten in mid-1995 and named PHP/FI Version 2. The
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FI came from another package Rasmus had written which interpreted
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html form data. He combined the Personal Home Page tools scripts
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with the Form Interpreter and added mSQL support and PHP/FI was
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born. PHP/FI grew at an amazing pace and people started
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contributing code to it.
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</simpara>
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<simpara>
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It is difficult to give any hard statistics, but it is estimated
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that by late 1996 PHP/FI was in use on at least 15,000 web sites
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around the world. By mid-1997 this number had grown to over
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50,000. Mid-1997 also saw a change in the development of PHP. It
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changed from being Rasmus' own pet project that a handful of
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people had contributed to, to being a much more organized team
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effort. The parser was rewritten from scratch by Zeev Suraski and
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Andi Gutmans and this new parser formed the basis for PHP Version
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3. A lot of the utility code from PHP/FI was ported over to PHP 3
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and a lot of it was completely rewritten.
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</simpara>
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<simpara>
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2001-01-12 23:36:02 +00:00
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The latest version (PHP 4) uses the <ulink
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url="&url.zend;">Zend</ulink> scripting engine to deliver higher
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performance, supports an even wider array of third-party libraries
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and extensions, and runs as a native server module with all of the
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popular web servers.
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</simpara>
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<simpara>
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Today (1/2001) PHP 3 or PHP 4 now ships with a number of
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commercial products such as Red Hat's Stronghold web server.
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A conservative estimate based on an extrapolation from
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numbers provided by <ulink url="&url.netcraft;">Netcraft</ulink>
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(see also <ulink url="&url.netcraft-survey;">Netcraft Web Server
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Survey</ulink>) would be that PHP is in use on over 5,100,000
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sites around the world. To put that in perspective, that is
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slightly more sites than run Microsoft's IIS server on the Internet
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(5.03 million).
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</simpara>
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<!--
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<figure>
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<title>NetCraft Webserver Survey</title>
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2000-02-02 13:54:20 +00:00
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<graphic fileref="&url.php.stats;"/>
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</figure>
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-->
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</sect1>
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</chapter>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode: sgml
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sgml-omittag:t
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sgml-shorttag:t
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sgml-minimize-attributes:nil
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sgml-always-quote-attributes:t
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sgml-indent-step:1
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sgml-indent-data:t
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sgml-parent-document:nil
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sgml-default-dtd-file:"../../manual.ced"
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sgml-exposed-tags:nil
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sgml-local-catalogs:nil
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sgml-local-ecat-files:nil
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End:
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vim600: syn=xml fen fdm=syntax fdl=2 si
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vim: et tw=78 syn=sgml
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vi: ts=1 sw=1
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-->
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