PHP 7 Quick Scripting Reference, 2nd Edition
PHP is a server-side programming language used for creating dynamic web sites and interactive web applications. The acronym PHP originally stood for Personal Home Page, but as its functionality grew, this was changed to PHP: Hypertext Preprocessor. This recursive acronym comes from the fact that it takes PHP code as input and produces HTML as output. This means that users do not need to install any software to view PHP-generated web pages. All that is required is that the web server has PHP installed to interpret the script. In contrast with HTML sites, PHP sites are dynamically generated. Instead of the site being made up of a large number of static HTML files, a PHP site may consist of only a handful of template files. The template files describe only the structure of the site using PHP code, while the web content is pulled from a database and the style formatting is from Cascading Style Sheets (CSS). This allows for site-wide changes from a single location, providing a flexible web site that is easy to design, maintain, and update. When creating web sites with PHP, a content management system (CMS) is generally used. A CMS provides a fully integrated platform for web site development consisting of a back end and a front end. The front end is what visitors see when they arrive at the site, whereas the back end is where the site is configured, updated, and managed by an administrator. The back end also allows a web developer to change template files and modify plugins to more extensively customize the functionality and structure of the site. Examples of free PHP-based CMS solutions include WordPress, Joomla, ModX, and Drupal, with WordPress being the most popular and accounting for more than half of the CMS market. The first version of PHP was created by Rasmus Lerdorf and released in 1995. Since then, PHP has evolved greatly from a simple scripting language to a fully featured web programming language. The official implementation is now released by The PHP Group, with PHP 7 being the most recent version as of this writing. The language may be used free of charge and is open source, allowing developers to extend it for their own use or to contribute to its development. PHP is by far the most popular server-side programming language in use today. It holds a growing 80% market share when compared with other server-side technologies, such as ASP.NET, Java, Ruby, and Perl. One of the reasons for the widespread adoption of PHP is its platform independence. It can be installed on all major web servers and operating systems, and used with any major database system.