You, as a developer of Web sites, do not have a choice in what PHP software to use; there is only one implementation of PHP worldwide. A computer called a server hosts your Web site and answers requests to provide pages for viewing. A copy of PHP software is installed for use by all the Web sites hosted on that server. PHP is a scripting language that augments hypertext markup language (HTML), used to create Web sites on the Internet. A scripting language is not a true programming language; rather, it modifies real-time online presentation of HTML content to provide current, dynamic information to the visitors of the Web site.
HTML is the language or computer coding that displays content, words, and pictures when someone types in the address for your Web site. The HTML coding tells the server and ultimately, your computer, what text and pictures to show and how to show it, such as in red bold type. This is the markup part of the HTML name. The hypertext part refers to the ability of HTML to provide links to other parts of your Web site or any site with an address on the Internet.
As useful as HTML is, all of the HTML Web site pages are static, meaning that each page always presents the same information, with very minor exceptions. The development of PHP software enabled the pages to become dynamic and allowed users to interact with the pages to provide customized information. PHP does this with PHP files residing on the server, with the Web site data in the same folders. Within the PHP file will be directions on how to get the variable data to display.
PHP software is a server-side preprocessor because it resides on the server and grabs the page from the server before the browser, the software that displays HTML code on your computer, can display it. When a server receives a request to display an HTML page, the PHP program reads the HTML code first, looks for pointers to PHP code, performs the PHP task, and writes that content into the HTML code. The server then passes the page with both the original and inserted content. Your browser interprets both the HTML and the PHP inserts as HTML.
Programmers from around the world contribute to the development and maintenance of PHP software. Among the most useful of the features of PHP is the ability to request information from a structured query database. Third-party developers provide graphical interfaces to reduce the effort to code PHP, in what is called integrated development environments (IDE). These IDE may include debuggers, stepwise execution, variable-watch, and other tools common to software coding.