PHP (Hypertext Preprocessor, recursively) is an open source general-purpose scripting language primarily meant for server-side web development purposes. However, it also a programming language and allows programming constructs to be created. It is known to work on all operating systems and is extensively used in web-based applications development.
PHP was created by Rasmus Lerdorf in 1994 and currently managed by The PHP Development Team. The team is responsible to issue PHP’s reference implementation which is released under BSD-style PHP License. The initial release of PHP happened in June 1995. The latest version, at the time of this writing, PHP 7.1.0 stable release was released in December 2016.
PHP is embedded into HTML to design dynamic and interactive webpages. It can be used with various web template systems, web content management systems and web frameworks. The PHP embedded code can include any kind of data such as text, image, video, etc. In PHP, unlike most other scripting languages, the embedded code is executed on the server, producing a HTML which is then sent to the client. A PHP Interpreter is generally responsible to process the code embedded in the HTML. The interpreter is a module in the web server or as a Common Gateway Interface (CGI) executable. The web server combines the results of the interpreted PHP code into the generated web page. The standard PHP interpreter using the Zend Engine, is also a free software also released under the PHP License. PHP also includes the Standard PHP Library (SPL) with functions to manipulate data, and work with classes and interfaces.
PHP allows its basis functionalities to be extended by adding PHP extensions. These extensions can be written in programming languages such as C or C++ and added to PHP applications to provide additional capabilities. They can be compiled statically into PHP or loaded dynamically at runtime. Popular extensions of PHP include PHP Data Objects (PDO) - to access databases, integration with IRC, dynamic generation of images and Adobe Flash content etc. PHP maintains all its extension with The PHP Extension Community Library (PECL) project.Some of the features of PHP include:
- A loosely typed language; data type not strictly applied.
- The PHP interpreter that executes PHP code within its delimiters.
- Allows declaration of variables and constants of different data types and with different access-specifiers. Also has predefined variables called super-globals.
- Allows creation of arrays of any type and character strings and supports extended regular expressions.
- Provides programming constructs as loops, functions, etc.
- Provides command-line interface also to execute PHP code.
- Allows creation of standard graphical applications.
- Supports object oriented PHP code with ability to create abstract classes, final classes, abstract methods, and final methods, interfaces, constructors and destructors.
- Provides extensions to work with MySQL and with many other relational database management systems (RDBMS).
- Works with almost all popular web-servers used currently.
- Allows file manipulations on server.
- Allows exception handling in the code and provides predefined error reporting constants.
- Supports internationalization of code.
- Supports usage of cookies.
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