The PHP WebSockets code hasn't been updated in a while and is no longer compatible with all browsers. You probably should not use it for production code.
PHP WebSockets is a PHP library that implements the WebSockets protocol. The WebSockets protocol (RFC6455) is currently being standardized by the IETF. With WebSockets, a client (e.g.: a browser) and a server can set up a two-way communication channel with little overhead compared to a XMLHttpRequest or long polling.