mirror of
https://github.com/sigmasternchen/php-doc-en
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09cf574276
Co-authored-by: Kamil Tekiela <tekiela246@gmail.com> Co-authored-by: Sergey Panteleev <sergey@php.net>
219 lines
9 KiB
XML
219 lines
9 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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<!-- $Revision$ -->
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<chapter xml:id="introduction" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
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<info><title>Introduction</title></info>
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<section xml:id="intro-whatis">
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<info><title>What is PHP?</title></info>
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<para>
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<acronym>PHP</acronym> (recursive acronym for <literal>PHP: Hypertext
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Preprocessor</literal>) is a widely-used open source general-purpose
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scripting language that is especially suited for web
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development and can be embedded into HTML.
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</para>
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<para>
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Nice, but what does that mean? An example:
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</para>
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<para>
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<example>
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<info><title>An introductory example</title></info>
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<programlisting role="php">
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<![CDATA[
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<!DOCTYPE html>
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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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<?php
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echo "Hi, I'm a PHP script!";
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?>
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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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<para>
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Instead of lots of commands to output HTML (as seen in C or Perl),
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PHP pages contain HTML with embedded code that does
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"something" (in this case, output "Hi, I'm a PHP script!").
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The PHP code is enclosed in special <link
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linkend="language.basic-syntax.phpmode">start and end processing
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instructions <code><?php</code> and <code>?></code></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, generating HTML which
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is then sent to the client. The client would receive
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the results of running that script, but would not know
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what the underlying code was. 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 part about using PHP is 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 to read the long
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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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or go right to the <link linkend="tutorial">introductory
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tutorial</link> if you are only interested in web programming.
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</para>
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</section>
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<section xml:id="intro-whatcando">
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<info><title>What can PHP do?</title></info>
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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 areas 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 web server and a web browser. You need to
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run the web server, 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. All these can
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run on your home machine if you are just experimenting
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with PHP programming. See the
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<link linkend="install">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 or 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 (on *nix or Linux) or Task Scheduler (on
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Windows). These scripts can also be used for simple text
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processing tasks. See the section about
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<link linkend="features.commandline">Command line usage of PHP</link>
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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 desktop applications. PHP is probably
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not the very best language to create a desktop
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application with a graphical user interface, but if
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you know PHP very well, and would like to use some
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advanced PHP features in your client-side applications
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you can also use PHP-GTK to write such programs. You also
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have the ability to write cross-platform applications this
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way. 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 <link xlink:href="&url.php.gtk;">its
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own website</link>.
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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 <link linkend="install">used</link> 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, macOS, RISC OS, and probably others.
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PHP also has support for most of the web servers today. This
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includes Apache, IIS, and many others. And this includes any
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web server that can utilize the FastCGI PHP binary, like lighttpd
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and nginx. PHP works as either a module, or 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 (OOP), or a mixture of them both.
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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 outputting 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 features in PHP is its
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support for a <link linkend="refs.database">wide range of databases</link>.
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Writing a database-enabled web page is incredibly simple using one of
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the database specific extensions (e.g., for <link linkend="book.mysqli">mysql</link>),
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or using an abstraction layer like <link linkend="book.pdo">PDO</link>, or connect
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to any database supporting the Open Database Connection standard via the
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<link linkend="book.uodbc">ODBC</link> extension. Other databases may utilize
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<link linkend="book.curl">cURL</link> or <link linkend="book.sockets">sockets</link>,
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like CouchDB.
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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.
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</para>
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<para>
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PHP has useful <link linkend="refs.basic.text">text processing</link> features,
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which includes the Perl compatible regular expressions (<link linkend="book.pcre">PCRE</link>),
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and many extensions and tools to <link linkend="refs.xml">parse and access XML documents</link>.
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PHP standardizes all of the XML extensions on the solid base of <link linkend="book.libxml">libxml2</link>,
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and extends the feature set adding <link linkend="book.simplexml">SimpleXML</link>,
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<link linkend="book.xmlreader">XMLReader</link> and <link linkend="book.xmlwriter">XMLWriter</link> support.
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</para>
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<para>
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And many other interesting extensions exist, which are categorized both
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<link linkend="extensions">alphabetically</link> and by <link linkend="funcref">category</link>.
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And there are additional PECL extensions that may or may not be documented
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within the PHP manual itself, like <link xlink:href="&url.xdebug;">XDebug</link>.
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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="install">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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</section>
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</chapter>
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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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indent-tabs-mode:nil
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sgml-parent-document:nil
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sgml-default-dtd-file:"~/.phpdoc/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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