Files with the extension PHP are Hypertext PreProcessor Script files.
PHP is a scripting language that runs on a web server, producing output in the form of HTML pages. PHP has many features that simplify collaboration with databases such as MySQL, and enables rich web applications such as MySQL. Develop content management systems.
Since PHP is an open source project, it is very widespread and used on many websites. The applications range from simple forms like a form to complex management systems and shops.
Files with the extension PHP can contain pure PHP source code as well as this embedded in an HTML. It is similar to ASP, CGI or JSP.
To edit a PHP file, just use a text editor. But there are also complete development environments, which greatly simplify the development of PHP scripts.
The extension PHP in a URL (in the address line of a browser) indicates that PHP is being used on the website. The user of the website receives only the PHP script generated HTML document not the actual PHP script.