What is Protocol Buffer and how i can use this in PHP ?

Protocol Buffers are a way of encoding structured data in an efficient yet extensible format. Google uses Protocol Buffers for almost all of its internal RPC protocols and file formats.

SOURCE: http://pecl.php.net/package/protocolbuffers

Protocol Buffers are a method of serializing structured data. As such, they are useful in developing programs to communicate with each other over a wire or for storing data. The method involves an interface description language that describes the structure of some data and a program that generates from that description source code in various programming languages for generating or parsing a stream of bytes that represents the structured data.

Google developed Protocol Buffers for use internally and has made protocol compilers for C++, Java and Python available to the public under a free software, open source license. Various other language implementations are also available.

SOURCE: http://en.wikipedia.org/wiki/Protocol_Buffers

To use Protocol Buffers in PHP there are several APIs on web. I found following useful.

https://github.com/datto/Protobuf-PHP

https://github.com/chobie/protoc-gen-php

On homepage of above APIs there are very good Installation/Usage instructions.

https://github.com/datto/Protobuf-PHP#example-usage

https://github.com/chobie/protoc-gen-php/tree/master/tests