To make use of fDebug a client as well as a server part needs to be used. While logically a client, the fdebug client app or extension is technically the server - waiting for debug information to arrive.
You can download a prebuild XPI from http://fdebug.de or https://addons.mozilla.org/de/firefox/addon/fdebug-client/.
Within the repository you can find a small shellscript to build an XPI. Simply change to the client directory and run it:
cd client/firefox/build
./build.sh
You will be asked for a version number for your XPI build. Please do not use any "offical" release version strings here when doing custom build to avoid confusion for other users in case you plan on shipping your (modified) XPI.
PHP version of the server code:
<?php
require 'fdebug.lib.php';
$fdebug = fDebug::getInstance();
$fdebug->setSession('localhost','example Request');
$fdebug->openSocket('127.0.0.1');
$fdebug->sendMessage("test\ntest\n\test!");
$fdebug->sendWarning('test');
$fdebug->sendVariables(array('Foo' => 'bar'), false);
$fdebug->sendSource('<?xml version="1.0" ?><root><foo/></root>');