The new version of the PHP programming language, PHP 4.1.0, includes several other key improvements: A new input interface for improved security (read below), Highly improved performance in general, Revolutionary performance and stability improvements under Windows. The multithreaded server modules under Windows (ISAPI, Apache, etc.) perform as much as 30 times faster under load! We want to thank Brett Brewer and his team in Microsoft for working with us to improve PHP for Windows. Versioning support for extensions. Right now it’s barely being used, but the infrastructure was put in place to support separate version numbers for different extensions. The negative side effect is that loading extensions that were built against old versions of PHP will now result in a crash, instead of in a nice clear message. Make sure you only use extensions built with PHP 4.1.0. Turn-key output compression support. Lots of fixes and new functions.