How to find out what the response time from the server consists of?

Question

PHP

I am writing a script to backup a site on one unpopular engine. To implement a backup through a button in the control panel, I use a series of AJAX requests, each of which puts hundreds of files into the archive. Thus, the problem of timeout in the work of the script and the response from the server is solved, plus the user has a visualization that does not allow him to be nervous.
The problem is that the response time for the next request is from 5 to 15 seconds, while the script itself is executed in less than a second. I measured the script's running time using two calls to microtime (true) - in the first line of the "entry point" to the engine and immediately after the output of my plugin.
The question is, where does the rest of the time go? How to check it?
Apache 2.2.22, PHP 5.5.4, run via mod_php.

Answer 1

I asked it myself, I answered it myself ... I messed up :-)
The bottom line is that I put microtime () in the wrong place. For archiving, I used ZipArchive, and measured the time it takes for ZipArchive::addFile(), but did not take into account ZipArchive::close(). But it is at the moment of closing that the file is written to.

Answer 2

On the client side - firebug or fiddler see.