php http pipeline

I'm trying to get timestamp on beginRequest and on endReques开发者_StackOverflow社区t when processing an http request using php. I know how to do it on asp.net (using httpModules and the finction beginRequest and endRequest). Does anyone know if this option is available on php and guide me how to do it? (I'm not looking for a solution, just some guiding or good reference because i couldn't find any...)

$_SERVER['REQUEST_TIME'] has the Unix timestamp of the request. If you want precise times, use microtime