He rewrote these scripts as C programming language Common Gateway Interface (CGI) binaries, extending them to add the ability to work with web forms and to communicate with databases and called this implementation 'Personal Home Page/Forms Interpreter' or PHP/FI. PHP/FI could be used to build simple, dynamic web applications. Lerdorf released PHP/FI as 'Personal Home Page Tools (PHP Tools) version 1.0' publicly on June 8, 1995, to accelerate bug location and improve the code.[6] This release already had the basic functionality that PHP has today. This included Perl-like variables, form handling, and the ability to embed HTML. The syntax was similar to Perl but was more limited and simpler, although less consistent.[3] A development team began to form and, after months of work and beta testing, officially released PHP/FI 2 in November 1997.
Zeev Suraski and Andi Gutmans, two Israeli developers at the Technion IIT, rewrote the parser in 1997 and formed the base of PHP 3, changing the language's name to the recursive initialism PHP: Hypertext Preprocessor.[3] Afterwards, public testing of PHP 3 began, 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.[7] They also founded Zend Technologies in Ramat Gan, Israel.[3]
On May 22, 2000, PHP 4, powered by the Zend Engine 1.0, was released.[3] As of August 2008 this branch is up to version 4.4.9. PHP 4 is no longer under development nor will any security updates be released.[8][9]
On July 13, 2004, PHP 5 was released, powered by the new Zend Engine II.[3] PHP 5 included new features such as improved support for object-oriented programming, the PHP Data Objects (PDO) extension (which defines a lightweight and consistent interface for accessing databases), and numerous performance enhancements.[10] In 2008 PHP 5 became the only stable version under development. Late static binding had been missing from PHP and was added in version 5.3.[11][12]
A new major version has been under development alongside PHP 5 for several years. This version was originally planned to be released as PHP 6 as a result of its significant changes, which included plans for full Unicode support. However, Unicode support took developers much longer to implement than originally thought, and the decision was made in March 2010[13] to move the project to a branch, with features still under development moved to a trunk.
Changes in the new code include the removal of register_globals,[14] magic quotes, and safe mode.[8][15] The reason for the removals was that register_globals had given way to security holes, and the use of magic quotes had an unpredictable nature, and was best avoided. Instead, to escape characters, magic quotes may be replaced with the addslashes() function, or more appropriately an escape mechanism specific to the database vendor itself like mysql_real_escape_string() for MySQL. Functions that will be removed in future versions and have been deprecated in PHP 5.3 will produce a warning if used.[16]
Many high-profile open-source projects ceased to support PHP 4 in new code as of February 5, 2008, because of the GoPHP5 initiative,[17] provided by a consortium of PHP developers promoting the transition from PHP 4 to PHP 5.[18][19]
PHP currently does not have native support for Unicode or multibyte strings; Unicode support is under development for a future version of PHP and will allow strings as well as class, method, and function names to contain non-ASCII characters.[20][21]
PHP interpreters are available on both 32-bit and 64-bit operating systems, but on Microsoft Windows the only official distribution is a 32-bit implementation, requiring Windows 32-bit compatibility mode while using Internet Information Services (IIS) on a 64-bit Windows platform. As of PHP 5.3.0, experimental 64-bit versions are available for MS Windows.[22]
[edit] Licensing
PHP is free software released under the PHP License, which insists that:
• The name "PHP" must not be used to endorse or promote products derived from this software without prior written permission.[23]
This makes it incompatible with the GNU General Public License (GPL) because restrictions exist regarding the use of the term PHP.[24]
[edit] Release history
[edit] Usage
PHP is a general-purpose scripting language that is especially suited to server-side web development where PHP generally runs on a web server. Any PHP code in a requested file is executed by the PHP runtime, usually to create dynamic web page content. It can also be used for command-line scripting and client-side GUI applications. PHP can be deployed on most web servers, many operating systems and platforms, and can be used with many relational database management systems. It is available free of charge, and the PHP Group provides the complete source code for users to build, customize and extend for their own use.[31]
PHP primarily acts as a filter,[32] taking input from a file or stream containing text and/or PHP instructions and outputs another stream of data; most commonly the output will be HTML. Since PHP 4, the PHP parser compiles input to produce bytecode for processing by the Zend Engine, giving improved performance over its interpreter predecessor.[33]
Originally designed to create dynamic web pages, PHP now focuses mainly on server-side scripting,[34] and it is similar to other server-side scripting languages that provide dynamic content from a web server to a client, such as Microsoft's Active Server Pages, Sun Microsystems' JavaServer Pages,[35] and mod_perl. PHP has also attracted the development of many frameworks that provide building blocks and a design structure to promote rapid application development (RAD). Some of these include CakePHP, Symfony, CodeIgniter, and Zend Framework, offering features similar to other web application frameworks.
The LAMP architecture has become popular in the web industry as a way of deploying web applications. PHP is commonly used as the P in this bundle alongside Linux, Apache and MySQL, although the P may also refer to Python or Perl or some combination of the three. WAMP packages (Windows/ Apache/ MySQL / PHP) are also available.
As of April 2007, over 20 million Internet domains had web services hosted on servers with PHP installed and mod_php was recorded as the most popular Apache HTTP Server module.[36] Significant websites are written in PHP including the user-facing portion of Facebook,[37] Wikipedia (MediaWiki),[38] Digg,[39] Joomla, eZ Publish, WordPress,[40] Drupal [41] and Moodle.[42]
[edit] Security
The National Vulnerability Database maintains a list of vulnerabilities found in computer software. The overall proportion of PHP-related vulnerabilities on the database amounted to: 20% in 2004, 28% in 2005, 43% in 2006, 36% in 2007, 35% in 2008, and 30% in 2009.[43] Most of these PHP-related vulnerabilities can be exploited remotely: they allow crackers to steal or destroy data from data sources linked to the webserver (such as an SQL database), send spam or contribute to DoS attacks using malware, which itself can be installed on the vulnerable servers.
These vulnerabilities are caused mostly by not following best practice programming rules: technical security flaws of the language itself or of its core libraries are not frequent (23 in 2008, about 1% of the total). [44][45] Recognizing that programmers cannot be trusted, some languages include taint checking to detect automatically the lack of input validation which induces many issues. Such a feature is being developed for PHP,[46] but its inclusion in a release has been rejected several times in the past.[47][48]
Hosting PHP applications on a server requires a careful and constant attention to deal with these security risks.[49] There are advanced protection patches such as Suhosin and Hardening-Patch, especially designed for web hosting environments.[50]
[edit] Syntax
Main article: PHP syntax and semantics
echo "Hello World";
/* echo("Hello World"); works as well, although echo isn't a
function, but a language construct. In some cases, such
as when multiple parameters are passed to echo, parameters
cannot be enclosed in parentheses. */
?>
PHP code embedded within HTML code
PHP only parses code within its delimiters. Anything outside its delimiters is sent directly to the output and is not processed by PHP (although non-PHP text is still subject to control structures described within PHP code). The most common delimiters are to close PHP sections. delimiters are also available, as are the shortened forms as well as ASP-style short forms <% or <%= and %>. While short delimiters are used, they make script files less portable as their purpose can be disabled in the PHP configuration, and so they are discouraged.[51] The purpose of all these delimiters is to separate PHP code from non-PHP code, including HTML.[52]
The first form of delimiters, , in XHTML and other XML documents, creates correctly formed XML 'processing instructions'.[53] This means that the resulting mixture of PHP code and other markup in the server-side file is itself well-formed XML.
Variables are prefixed with a dollar symbol and a type does not need to be specified in advance. Unlike function and class names, variable names are case sensitive. Both double-quoted ("") and heredoc strings allow the ability to embed a variable's value into the string.[54] PHP treats newlines as whitespace in the manner of a free-form language (except when inside string quotes), and statements are terminated by a semicolon.[55] PHP has three types of comment syntax: /* */ marks block and inline comments; // as well as # are used for one-line comments.[56] The echo statement is one of several facilities PHP provides to output text (e.g. to a web browser).
In terms of keywords and language syntax, PHP is similar to most high level languages that follow the C style syntax. If conditions, for and while loops, and function returns are similar in syntax to languages such as C, C++, Java and Perl.
[edit] Data types
PHP stores whole numbers in a platform-dependent range. This range is typically that of 32-bit signed integers. Unsigned integers are converted to signed values in certain situations; this behavior is different from other programming languages.[57] Integer variables can be assigned using decimal (positive and negative), octal, and hexadecimal notations. Floating point numbers are also stored in a platform-specific range. They can be specified using floating point notation, or two forms of scientific notation.[58] PHP has a native Boolean type that is similar to the native Boolean types in Java and C++. Using the Boolean type conversion rules, non-zero values are interpreted as true and zero as false, as in Perl and C++.[58] The null data type represents a variable that has no value. The only value in the null data type is NULL.[58] Variables of the "resource" type represent references to resources from external sources. These are typically created by functions from a particular extension, and can only be processed by functions from the same extension; examples include file, image, and database resources.[58] Arrays can contain elements of any type that PHP can handle, including resources, objects, and even other arrays. Order is preserved in lists of values and in hashes with both keys and values, and the two can be intermingled.[58] PHP also supports strings, which can be used with single quotes, double quotes, or heredoc syntax.[59]
The Standard PHP Library (SPL) attempts to solve standard problems and implements efficient data access interfaces and classes.[60]
[edit] Functions
PHP has hundreds of base functions and thousands more via extensions. These functions are well documented on the PHP site; however, the built-in library has a wide variety of naming conventions and inconsistencies. PHP currently has no functions for thread programming, although it does support multiprocess programming on POSIX systems.[61]
[edit] 5.2 and earlier
Functions are not first-class functions and can only be referenced by their name, directly or dynamically by a variable containing the name of the function.[62] User-defined functions can be created at any time without being prototyped.[62] Functions can be defined inside code blocks, permitting a run-time decision as to whether or not a function should be defined. Function calls must use parentheses, with the exception of zero argument class constructor functions called with the PHP new operator, where parentheses are optional. PHP supports quasi-anonymous functions through the create_function() function, although they are not true anonymous functions because anonymous functions are nameless, but functions can only be referenced by name, or indirectly through a variable $function_name();, in PHP.[62]
[edit] 5.3 and newer
PHP gained support for closures. True anonymous functions are supported using the following syntax:
function getAdder($x) {
return function ($y) use ($x) {
return $x + $y;
};
}
$adder = getAdder(8);
echo $adder(2); // prints "10"
Here, the getAdder() function creates a closure using the parameter $x (the keyword "use" imports a variable from the lexical context), which takes an additional argument $y and returns it to the caller. Such a function is a first class object, that means, it can be stored, passed as a parameter to other functions, etc. For more details see Lambda functions and closures RFC.
The goto flow control statement is used as follows:
function lock() {
$file = fopen('file.txt', 'r+');
retry:
if (!flock($file, LOCK_EX)) {
goto retry;
}
fwrite($file, 'Success!');
fclose($file);
return 0;
}
When lock() is called, PHP opens a file and tries to lock it. retry:, the target label, defines the point to which execution should return if flock() is unsuccessful and the goto retry; is called. goto is restricted and requires that the target label be in the same file and context.
[edit] Objects
Basic object-oriented programming functionality was added in PHP 3 and improved in PHP 4.[3] Object handling was completely rewritten for PHP 5, expanding the feature set and enhancing performance.[63] In previous versions of PHP, objects were handled like value types.[63] The drawback of this method was that the whole object was copied when a variable was assigned or passed as a parameter to a method. In the new approach, objects are referenced by handle, and not by value. PHP 5 introduced private and protected member variables and methods, along with abstract classes and final classes as well as abstract methods and final methods. It also introduced a standard way of declaring constructors and destructors, similar to that of other object-oriented languages such as C++, and a standard exception handling model. Furthermore, PHP 5 added interfaces and allowed for multiple interfaces to be implemented. There are special interfaces that allow objects to interact with the runtime system. Objects implementing ArrayAccess can be used with array syntax and objects implementing Iterator or IteratorAggregate can be used with the foreach language construct. There is no virtual table feature in the engine, so static variables are bound with a name instead of a reference at compile time.[64]
If the developer creates a copy of an object using the reserved word clone, the Zend engine will check if a __clone() method has been defined or not. If not, it will call a default __clone() which will copy the object's properties. If a __clone() method is defined, then it will be responsible for setting the necessary properties in the created object. For convenience, the engine will supply a function that imports the properties of the source object, so that the programmer can start with a by-value replica of the source object and only override properties that need to be changed.[65]
Basic example of object-oriented programming as described above:
class Person {
public $first;
public $last;
public function __construct($f, $l) {
$this->first = $f;
$this->last = $l;
}
public function greeting() {
return "Hello, my name is {$this->first} {$this->last}.";
}
static public function staticGreeting($first, $last) {
return "Hello, my name is {$first} {$last}.";
}
}
$him = new Person('John', 'Smith');
$her = new Person('Sally', 'Davis');
echo $him->greeting(); // prints "Hello, my name is John Smith."
echo '
';
echo $her->greeting(); // prints "Hello, my name is Sally Davis."
echo '
';
echo Person::staticGreeting('Jane', 'Doe'); // prints "Hello, my name is Jane Doe."
[edit] Visibility of properties and methods
The visibility of PHP properties and methods refers to visibility in PHP. It is defined using the keywords "public," "private," and "protected." The default is public, if only var is used; "var" is a synonym for "public." Public declared items can be accessed everywhere. Protected limits access to inherited classes (and to the class that defines the item). Private limits visibility only to the class that defines the item.[66] Objects of the same type have access to each others private and protected members even though they are not the same instances. PHP's member visibility features have sometimes been described as "highly useful."[67] However, they have also sometimes been described as "at best irrelevant and at worst positively harmful."[68]
[edit] Speed optimization
PHP source code is compiled on-the-fly to an internal format that can be executed by the PHP engine.[69][70] In order to speed up execution time and not have to compile the PHP source code every time the webpage is accessed, PHP scripts can also be deployed in executable format using a PHP compiler.
Code optimizers aim to reduce the runtime of the compiled code by reducing its size and making other changes that can reduce the execution time with the goal of improving performance. The nature of the PHP compiler is such that there are often opportunities for code optimization,[71] and an example of a code optimizer is the eAccelerator PHP extension.[72]
Another approach for reducing overhead for high load PHP servers is using an opcode cache. Opcode caches work by caching the compiled form of a PHP script (opcodes) in shared memory to avoid the overhead of parsing and compiling the code every time the script runs. An opcode cache, APC, will be built into an upcoming release of PHP.[73] Opcode caching is also available in Zend Server Community Edition.
[edit] Compilers
The PHP language was originally implemented using a PHP interpreter. Several compilers now exist, which decouple the PHP language from the interpreter:
• phc - a C++ based compiler for PHP, using the Zend run-time for maximum compatibility
• Roadsend - achieves native compilation by compiling to bigloo scheme, which in turn is compiled to C, then to machine code
• Raven - a rewrite of Roadsend PHP (rphp), based on LLVM and a new C++ runtime
• Phalanger - compiles source code written in the PHP scripting language into CIL byte-code
• Caucho Resin/Quercus - compiles PHP to Java bytecode
• HipHop - developed at Facebook and now available as open source, transforms the PHP Script into C++, then compiles it.
• php-to-scala - converts PHP to human-readable Scala source code, which the developer can compile to Java bytecode
Advantages of compilation include not only better execution speed, but also obfuscation, static analysis, and improved interoperability with code written in other languages.[74]
[edit] Resources
PHP includes free and open source libraries with the core build. PHP is a fundamentally Internet-aware system with modules built in for accessing FTP servers, many database servers, embedded SQL libraries such as embedded PostgreSQL, MySQL and SQLite, LDAP servers, and others. Many functions familiar to C programmers such as those in the stdio family are available in the standard PHP build.[75]
PHP allows developers to write extensions in C to add functionality to the PHP language. These can then be compiled into PHP or loaded dynamically at runtime. Extensions have been written to add support for the Windows API, process management on Unix-like operating systems, multibyte strings (Unicode), cURL, and several popular compression formats. Some more unusual features include integration with Internet Relay Chat, dynamic generation of images and Adobe Flash content, and even speech synthesis. The PHP Extension Community Library (PECL) project is a repository for extensions to the PHP language.[76]
[edit] Background of phpWebSite
PhpWebSite began with the release of version 0.7.0 on January 29, 2001 as a fork of Phpnuke.
PhpWebSite 0.8.x implemented broad changes to Phpnuke, including the ability to install modules.
A complete rewrite of the phpWebSite began in March 2002. The goals were to remove all Phpnuke code, increase modularity, and allow multiple installs to run off a single hub of code. The developers released the rewrite as phpWebsite 0.9.0 stable on February 2, 2003.
0.10.0 was released on November 24, 2005. It contained the same core as 0.9.x, but new default modules, themes, features and bug fixes. The final release in this series was 0.10.2, which was not compatible with php5. An unreleased version .11 fixed compatibility issues, but development on this series has ceased.
PhpWebSite 1.x (codename:Fallout) began development in 2003 with the core and core modules rewritten again for new functionality and ease-of-use issues. The first edition 1.0.0 has been available since November 2006. The current version is 1.6.3, released in June 2009.
[edit] Features of phpWebSite
PhpWebSite is programmed using the PHP scripting language and utilizes PHP Extension and Application Repository (or PEAR) libraries. Versions 0.7.x to 0.10.x require a MySQL database. PhpWebSite 1.x.x supports PostgreSQL as well. It was written to run under the Apache HTTP Server.
PhpWebSite is a content management system (CMS) which is often used by community groups and education users. Although offered to the public, its focus is serving Appalachian State University. Electronic Student Services (ESS), a department at Appalachian State, developed phpWebSite to make it easier for staff to build and update their web sites. ESS also wished to standardize the Student Development web presence and make sure it complied with the Web Accessibility Initiative (WAI).
PhpWebSite is a customizable, modular package; each component can be installed, updated, or modified by the phpWebSite administrator. PhpWebSite extends the customization to the user with selectable themes and HTML templates.
Although PhpWebSite modules cover functions like blogging, photo galleries, and bulletin boards, they often are not as feature-rich as dedicated web programs such as Word Press, Gallery Project, or phpBB. ESS focuses on the core library files in order to ease internal module development. Since many modules focus on university users, the content modules suffer in complexity.
For more information, see the Features page at http://phpwebsite.appstate.edu/.
[edit] Major Components
phpWebSite provides components in these general categories:
[edit] Content Creation and Management Tools
These features enable administrators and users to create, display, and maintain online-accessible content including text, documents, files, images, links, and more.
[edit] Content Organization Tools and Navigation Aids
These features enable administrators and users to organize, structure, and present content in a manageable way.
[edit] Communication Tools
These features enable administrators and users to communicate with each other (and the outside world) by means of numerous media, including internal messaging, email, data interchange, and more.
[edit] Configuration Tools and Administration Tools
These features enable administrators (and users who have been given the appropriate permissions) to configure and administer all aspects of a phpWebSite site.
phpWebsite utilizes a control panel approach to manage content and administer the system. Permissions are granular meaning general content contributors have no access to the administrative functions.
There is some work to be done prior to installing, but phpWebsite does checks for you to determine if your version of PHP meets the minimum requirements and whether certain features are enabled/disabled. Once you get past that initial screen, installing is nearly automatic. phpWebsite requires a backend database, most commonly used is MySQL.
[edit] Development Tools
These features enable administrators (and users who have been given the appropriate permissions) to develop modules for phpWebSite.
In addition, phpWebSite allows each user to choose from several different pre-defined visual styles/themes/skins. These themes are implemented using CSS and template files. Additional themes can be created by the phpWebSite administrator for branding or customizing the look of their website. This requires familiarity with CSS and templates. There are a number of themes to choose from and these can be previewed online. A large proportion of the themes are free to download and use. Commercial themes exist for purchase and commercial theme design services are also available.
[edit] Third Party Tools
A large number of third party modules exist for phpWebSite. These tools extend the capabilities of phpWebSite and because it uses an object-oriented framework the modules work together to build a customized CMS. These modules include tools across all major component categories and are constantly being updated and extended by the developer community. For more information, an extensive listing of third party modules can be found on the official phpWebSite web site.
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