PHP 5.1.6

   PHP: Hypertext Preprocessor is a general-purpose programming language originally designed for web development.

Vary Header check for User-Agent

   When using the Vary: User-Agent header, caching servers should consider the user agent when deciding whether to serve the page from cache

Gzip Content-Encoding

   The Content-Encoding entity header is used to compress the media-type. When present, its value indicates which encodings were applied to the entity-body. It lets the client know how to decode in order to obtain the media-type referenced by the Content-Type header.

Chunked transfer encoding

   Chunked transfer encoding is a streaming data transfer mechanism available in version 1.1 of the Hypertext Transfer Protocol (HTTP). In chunked transfer encoding, the data stream is divided into a series of non-overlapping "chunks"

Apache 2.0.52 |Operating System:CentOS

   The Apache HTTP Server, colloquially called Apache, is free and open-source cross-platform web server software, released under the terms of Apache License 2.0. Apache is developed and maintained by an open community of developers under the auspices of the Apache Software Foundation.