HTML, an initialism of HyperText Markup Language, is the predominant markup language for web pages. It provides a means to describe the structure of text-based information in a document — by denoting certain text as links, headings, paragraphs, lists, and so on — and to supplement that text with interactive forms, embedded images, and other objects. HTML is written in the form of tags, surrounded by angle brackets. HTML can also describe, to some degree, the appearance and semantics of a document, and can include embedded scripting language code (such as JavaScript) which can affect the behavior of Web browsers and other HTML processors.
HTML is also often used to refer to content of the MIME type text/html or even more broadly as a generic term for HTML whether in its XML-descended form (such as XHTML 1.0 and later) or its form descended directly from SGML (such as HTML 4.01 and earlier).
By convention, html format data files use a file extension .html or .htm.
PHP
PHP (PHP: Hypertext Preprocessor) is a computer scripting language, originally designed for producing dynamic web pages. It is mainly used in server-side scripting, but can be used from a command line interface or in standalone graphical applications.
While PHP was originally created by Rasmus Lerdorf in 1994, the main implementation of PHP is now produced by The PHP Group and serves as the de facto standard for PHP as there is no formal specification. Released under the PHP License, the Free Software Foundation considers it to be free software.
PHP is a widely-used general-purpose scripting language that is especially suited for web development and can be embedded into HTML. It generally runs on a web server, taking PHP code as its input and creating web pages as output. It can be deployed on most web servers and on almost every operating system and platform free of charge. PHP is installed on more than 20 million websites and 1 million servers, although the number of websites with PHP installed has declined since August 2005. It is also the most popular Apache module among computers using Apache as a web server. The most recent major release of PHP was version 5.2.0 on November 2, 2006.