PHP (Hypertext Preprocessor) is a server-side programming language used to create dynamic and interactive websites. It is a popular choice for web development because it is easy to learn and use and integrates well with databases such as MySQL.

PHP code runs on the server rather than in the user's web browser, which makes it a good choice for creating websites and applications that require server-side processing. For example, PHP can be used to create a form on a website that allows users to enter data that is then stored in a database or used to generate a personalised response.

PHP is often used in combination with HTML and CSS to create the front end of a website, and it can be integrated into a variety of content management systems (CMS) such as WordPress, Drupal and Joomla.

Overall, PHP is a widely used and powerful tool for web development, and it is an important skill for many web developers to learn.