What is xhp?

XHP is a PHP extension that simplifies the creation and manipulation of XML documents in PHP. It was created by Facebook as part of their PHP development efforts and is included in their open-source PHP library called the HipHop Virtual Machine. XHP provides a more object-oriented approach to working with XML, allowing developers to create and manipulate XML documents using familiar PHP classes and functions. It also includes a number of built-in security features that help protect against common XML-related vulnerabilities. XHP is widely used in a number of popular PHP frameworks and open-source projects, and is considered one of the most powerful and versatile PHP XML libraries available.