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<?xml version="1.0" encoding="iso-8859-1"?>
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<!-- $Revision: 1.24 $ -->
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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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2001-11-10 11:57:06 +00:00
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<para>
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PHP (recursive acronym for "PHP: Hypertext Preprocessor")
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is an open-source server-side HTML-embedded scripting language.
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</para>
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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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2001-11-09 15:48:16 +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 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 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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<para>
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The best things in using PHP are that it is extremely simple
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for a newcomer, but offers many advanced features for
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a professional programmer. Don't be afraid reading the long
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2001-11-10 13:36:43 +00:00
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list of PHP's features. You can jump in, in a short time, and
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start writing simple scripts in a few hours.
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</para>
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<para>
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Although PHP's development is focused on server-side scripting,
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you can do much more with it. Read on, and see more in the
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<link linkend="intro-whatcando">What can PHP do?</link> section.
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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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Anything. PHP is mainly focused on server-side scripting,
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so you can do anything any other CGI program can do, such
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as collect form data, generate dynamic page content, or
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send and receive cookies. But PHP can do much more.
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</para>
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<para>
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There are three main fields where PHP scripts are used.
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<itemizedlist>
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<listitem>
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<simpara>
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Server-side scripting. This is the most traditional
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and main target field for PHP. You need three things
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to make this work. The PHP parser (CGI or server
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module), a webserver and a web browser. You need to
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run the webserver, with a connected PHP installation.
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You can access the PHP program output with a web browser,
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viewing the PHP page through the server. See the
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<link linkend="installation">installation instructions</link>
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section for more information.
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</simpara>
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</listitem>
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<listitem>
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<simpara>
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Command line scripting. You can make a PHP script
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to run it without any server and any browser.
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You only need the PHP parser to use it this way.
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This type of usage is ideal for scripts regularly
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executed using cron (task sheduler on Windows),
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or simple text processing tasks. See the section about
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<link linkend="commandline">Command line usage
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of PHP</link> for more information.
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</simpara>
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</listitem>
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<listitem>
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<simpara>
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Writing client-side GUI applications. PHP is probably
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not the very best language to write windowing
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applications, but if you know PHP very well, and
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would like to use some advanced PHP features in
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your client-side applications you can also use
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PHP-GTK to write such programs. You also have the
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ability to write cross-platform applications this way.
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PHP-GTK is an extension to PHP, not available in
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the main distribution. If you are interested
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in PHP-GTK, visit <ulink url="&url.php.gtk;">it's
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own website</ulink>.
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</simpara>
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</listitem>
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</itemizedlist>
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</para>
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<para>
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PHP can be used on all major operating systems, including
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Linux, many Unix variants (including HP-UX, Solaris and OpenBSD),
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Microsoft Windows, Mac OS X, RISC OS, and probably others.
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PHP has also support for most of the web servers today. This
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includes Apache, Microsoft Internet Information Server,
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Personal Web Server, Netscape and iPlanet servers, Oreilly
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Website Pro server, Caudium, Xitami, OmniHTTPd, and many
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others. For the majority of the servers PHP has a module,
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for the others supporting the CGI standard, PHP can work
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as a CGI processor.
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</para>
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<para>
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So with PHP, you have the freedom of choosing an operating
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system and a web server. Furthermore, you also have the choice
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of using procedural programming or object oriented
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programming, or a mixture of them. Although not every
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standard OOP feature is realized in the current version
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of PHP, many code libraries and large applications (including the
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<link linkend="pear">PEAR library</link>) are written only
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using OOP code.
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</para>
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<para>
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With PHP you are not limited to output HTML. PHP's abilities
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includes outputing images, PDF files and even Flash movies
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(using libswf and Ming) generated on the fly. You can also
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output easily any text, such as XHTML and any other XML file.
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PHP can autogenerate these files, and save them in the file
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system, instead of printing it out, forming a server-side
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cache for your dynamic content.
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</para>
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<para>
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One of 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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We also have a DBX database abstraction extension allowing you
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to transparently use any database supported by that extension.
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Additionally PHP supports ODBC, the Open Database Connection
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standard, so you can connect to any other database supporting
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this world standard.
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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 LDAP, IMAP, SNMP, NNTP, POP3, HTTP, COM (on Windows) and
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countless others. You can also open raw network sockets and
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interact using any other protocol. PHP has support for the WDDX
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complex data exchange between virtually all Web programming
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languages. Talking about interconnection, PHP has support for
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instantiation of Java objects and using them transparently
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as PHP objects. You can also use our CORBA extension to
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access remote objects.
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</para>
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<para>
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PHP has extremely useful text processing features, from the
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POSIX Extended or Perl regular expressions to parsing XML
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documents. For parsing and accessing XML documents, we
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support the SAX and DOM standards. You can use our XSLT
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extension to transform XML documents.
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</para>
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<para>
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While using PHP in the ecommerce field, you'll find
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the Cybercash payment, CyberMUT, Verysign Payflow
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Pro and CCVS functions useful for your online payment
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programs.
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</para>
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<para>
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At last but not least, we have many other interesting
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extensions, the mnoGoSearch search engine functions,
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the IRC Gateway functions, many compression utilities
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(gzip, bz2), calendar conversion, translation...
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</para>
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<para>
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As you can see this page is not enough to list all
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the features and benefits PHP can offer. Read on in
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the sections about <link linkend="installation">installing
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PHP</link>, and see the <link linkend="funcref">function
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reference</link> part for explanation of the extensions
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mentioned here.
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</para>
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1999-12-19 17:16:54 +00:00
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</sect1>
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1999-06-06 18:51:02 +00:00
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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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1999-06-06 18:51:02 +00:00
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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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1999-12-19 17:16:54 +00:00
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(see also <ulink url="&url.netcraft-survey;">Netcraft Web Server
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2001-01-12 23:36:02 +00:00
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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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2001-01-13 00:50:35 +00:00
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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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1999-12-19 17:16:54 +00:00
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</simpara>
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2000-06-07 16:49:38 +00:00
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<!--
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1999-12-19 17:16:54 +00:00
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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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1999-12-19 17:16:54 +00:00
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</figure>
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2000-06-07 16:49:38 +00:00
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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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1999-06-06 18:51:02 +00:00
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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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1999-12-19 17:16:54 +00:00
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sgml-default-dtd-file:"../../manual.ced"
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1999-06-06 18:51:02 +00:00
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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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2001-09-21 22:47:49 +00:00
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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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1999-06-06 18:51:02 +00:00
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-->
|
