Microsoft FastCGI Extension for IIS

The IIS FastCGI Extension enables popular application frameworks like PHP be hosted on the IIS web server in a high-performance and reliable way.

FastCGI provides a high-performance alternative to the Common Gateway Interface (CGI), a standard way of interfacing external applications with Web servers that has been supported as part of the IIS feature-set since the very first release.

Most applications built to for IIS take advantage of the native, multi-threaded extensibility model of IIS. Many popular applications, particularly those written or originally designed for Linux, are not multi-threaded, and instead take a multi-process approach to concurrency.

While the PHP engine itself is multi-thread capable, many of the popular PHP extensions are not, requiring a single concurrent request guarantee to operate reliably.

This forces the use of CGI and results in poor performance on the Windows platform. FastCGI helps these application frameworks to achieve improved performance on Windows over CGI, while allowing stable operation in production environments.