PHP Shell is a simple Web-based environment for writing and testing PHP scripts in the most direct and straightforward way. It can be used in programming classes or in tandem with such web server stacks as XAMPP. PHP Shell is implemented as a Java Servlet and its source code is given in the form of NetBeans IDE's project. So you need to have JDK 7 (or higher), NetBeans IDE and Apache Tomcat servlet container installed on your machine.
For more information, read UserGuide.html in the project's root directory.