 |
|
| ||||||||||||||||||||||||||
|
|
| ||||||||||||||||||||||||||
|
|
|
|
|
| ||||||||
PHP (a recursive acronym for "PHP: Hypertext Preprocessor") is a widely-used open-source programming language primarily for server-side applications and developing dynamic web content. Famous examples of PHP applications include phpBB and MediaWiki, the software behind BambooWeb. The PHP model can be seen as an alternative to Microsoft's ASP/VBScript/JScript system, Sun Microsystems' JSP/Java system, and to the CGI/Perl system.
PHP's ease of use and similarity with the most common structured programming languages – most notably C and Perl (and from version 5, Java) – allows most experienced programmers to start developing complex applications with a minimal learning curve. It also enables experienced developers to get involved with dynamic web content applications without having to learn a whole new set of functions and practices.
One of the more attractive parts of PHP is that it is more than just a scripting language. Thanks to its modular design, PHP is also used to develop GUI applications (using PHP-GTK), and can be used from the command line just like Perl or Python.
PHP allows easy interaction with a large number of relational database systems, such as Oracle, DB2, MySQL, and PostgreSQL, while maintaining a simple and straightforward syntax. PHP runs on most major operating systems, including UNIX, Linux, Windows, and Mac OS X, and can interact with many major web servers. The contains . The Linux, Apache, MySQL, PHP (LAMP) architecture has become very popular in the Web industry as a way of deploying inexpensive, reliable, scalable, secure web applications. (The 'P' in LAMP can also stand for Perl or Python.)
PHP is the result of the collective efforts of many contributors. It is licensed under a BSD-style license, the PHP license. PHP, from version 4, has been powered by the Zend engine.
PHP was originally designed as a small set of Perl scripts, followed by a rewritten set of CGI binaries written in C by Rasmus Lerdorf in 1994 to display his résumé and collect some data, such as how many hits it was generating. Others first used "Personal Home Page Tools" in 1995, when Lerdorf had combined it with his own Form Interpreter to create PHP/FI. Zeev Suraski and Andi Gutmans, two Israeli developers of the Technion - Israel Institute of Technology, rewrote the parser in 1997 and formed the base of PHP 3. They also changed the name to its current recursive form. After months in beta, the development team officially released PHP/FI 2 in November 1997. Public testing of PHP 3 began immediately and the official launch came in June 1998. Suraski and Gutmans then started a new rewrite of PHP's core, producing the Zend engine in 1999 (a page at www.zend.com states that PHP 3 was powered by Zend Engine 0.5). In May 2000, PHP 4, powered by the Zend Engine 1.0, was released. On July 13, 2004, PHP 5 was released, powered by Zend Engine II (formerly known as Zend Engine 2).
PHP is currently one of the most popular server-side scripting systems on the Web. It has been widely adopted since the release of version 4, which was the first version powered by the powerful Zend Engine.
One major part of PHP which has helped it become popular is that it is a very loose language; in particular, it is dynamically typed. That is, the rules aren't as strict with variables—they don't have to be declared and they can hold any type of object. Further, unlike many other languages (like C++ and Java), arrays are able to hold objects of varying types, including other arrays. All of this "looseness" makes it very easy to do many things.
According to Netcraft's April 2002 survey, PHP is now the most deployed server-side scripting language, running on around 9 of the 37 million domains in their survey. This is confirmed by PHP's own figures, which show PHP usage (measured on a per-domain basis) growing at around 5% per month. In May 2003, almost 13 million domains were using PHP, based on the same source.
Due to PHP's popularity, a new breed of programmer has emerged – one who is only familiar with PHP, which in turn forced open the door toward a command line interface for PHP, along with support for GUI library such as GTK+ and text mode libraries like ncurses and newt. This is a major step for PHP, because it represents its beginning adoption as a genuine programming language (i.e. running autonomously on a stand-alone machine, as opposed to its original purpose of serving web pages to client machines from a server).
Here is an example that prints out the lyrics for the 99 bottles of beer -song:
<?php
/*
* This is a comment. Other ways of commenting are // and # symbols.
* This /* kind of comment does not need stars (*) in the beginning of
* each line but it's a good practice. // and # comments only comment
* the text that are after them in the same line and have no special
* ending character.
*/
/*
* First we define a new function called "plural".
* It will return an "s" if the argument passed to it was any other
* than number 1.
*/
function plural($number) {
return ($number != 1 ? "s" : "");
//This is a special way of creating an if-structure: (condition ? true : false).
}
//We define a variable called $l to contain an html line break
//as well as a carriage return and line feed:
$l = "<br />\r\n";
for( $i=99; $i>0; $i-- ) {
print "$i bottle".plural($i)." of beer on the wall,$l";
//We don't actually need a new print for each line. Let's see:
print "$i bottle".plural($i)." of beer.$l
Take one down, pass it around,$l".
($i-1 != 0 ? $i-1. : "no more").
" bottle".plural($i-1)." of beer on the wall.$l$l";
/*
* PHP does not mind if you cut a sentence in the middle as long as
* it finds a semicolon (;) to terminate it.
* A period (.) joins strings together. Variables, the $-symbol
* things, are parsed inside double quotation marks (") but wouldn't
* be parsed inside single quotation marks ('). Functions, such as
* plural(), are not parsed inside any quotation marks.
*/
}
print "Go to the store,$l buy some more,$l 99 bottles of beer on the wall!";
?>
PHP, unlike ASP, has some of the largest free and open-source libraries included with the core build. PHP is a fundamentally Internet-aware system and as such, there are modules built in for accessing FTP servers, all manners of database servers, embedded SQL libraries like embedded MySQL and SQLite, LDAP servers and much more. In addition to this, many familiar C functions such as the printf family are all available in the standard PHP build.
PHP has a wide variety of extensions such as support for the Windows API, process management on UNIX-like operating systems, cURL, and the ZIP/gzip/bzip2/rar/lzf compression formats. Some of the more unusual features are PDF generation, on-the-fly Macromedia Flash generation, integration with Internet relay chat and much more. Some additional extensions are available via the PHP Extension Community Library (PECL).
This is the present list of all officially documented libraries:
(Source: )
Up until version 3, PHP had no object-oriented features. In version 3 basic object functionality was added. The same semantics were implemented in PHP 4 as well as pass-by-reference and objects has been completely rewritten, allowing for better performance and more features. In previous versions of PHP, objects were handled like primitive types (for instance integers and strings). The drawback of this method was that semantically the whole object was copied when a variable was assigned, or pass as a parameter to a method. In the new approach, objects are referenced by handle, and not by value (one can think of a handle as an object's identifier).
PHP is widely used and widely admired for the tasks it performs. Like any language, however, it has its detractors. Some of the more common criticisms of PHP are as follows:
Criticism of PHP also includes those general criticisms ascribed to other scripting programming languages and dynamically typed languages.
Although the PHP development team does not provide programming help directly, there are many excellent help resources available for the novice PHP programmer. Worth mentioning are the (also available on [news://news.php.net/ PHP.net's news server]), the Usenet group comp.lang.php, and the IRC channels #php and #phphelp on EFNet, IRCNet, DALnet and other networks. There is also a . Other IRC channels include [irc://irc.freenode.net/php #php] and [irc://irc.freenode.net/php #phpfreaks] on freenode and also [irc://irc.invisionize.com/phpcafe #phpcafe] on irc.invisionize.com.
The following is list of notable software developed using PHP that's not already noted above: CMSformE, Drupal, Gallery Project, Invision Power Board, Moodle, PhpLDAPadmin, phpMyAdmin, PHP-Nuke, phpPgAdmin, PhpWiki, Pmachine, PmWiki, PostNuke, Smarty, UBB.threads, VBulletin, WordPress, Xaraya, XOOPS.
|
||||
| View Live Article | This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License | |
||