First, check that it isn’t actually working for you, and you don’t notice. I’ve done this…convinced it’s not working I wasted a chunk of time trying to get it to work, only to find that everything was OK.
Look at your NetBeans status bar. If you see "netbeans-xdebug" and "running" then it is actually working just fine. You probably have the "Stop at first line" option turned off and you didn’t hit any breakpoints you set (if any) yet. That would be a reason you are seeing the page with little or no indication that the debugger is actually connected.
If you instead see "Waiting for Connection (netbeans-xdebug)" and the progress bar is cycling, then you are indeed not connected. Open Tools|Options, and go to the PHP page. On the general tab, make sure that the "Debugger port" is 9000 and the "Session ID" is "netbeans-xdebug". You may want to have "Stop at First Line" checked. I don’t, as I find it a bit annoying. I would definitely ensure that "Watches and Balloon Evaluation" is not checked. This option causes NetBeans and the debugger to destabilize. If you need a watch, hack a local variable into the PHP code where you need it, and you’ll see it on the "Variables" tab when the debugger is running.
Since you see xdebug in phpinfo(), that end of it is fine. Just make sure that all of the values look reasonable, and that there is some reference to a cookie "XDEBUG_SESSION=netbeans-xdebug" somewhere on that page. (Make sure that you don’t have cookies turned off on the browser!)
The only other thing to check is to see if some firewall/security program is running that would be blocking TCP/UDP locally (which would be super-odd, but not out of the realm of possibility), or that port 9000 isn’t already used by another application. I am using a different port number in my local setup for some reason. I don’t remember changing it, but I am sure that the only reason I would have is if I had hit a port conflict with something else.
One last thing… We’ve been assuming that you are running NetBeans and the web server on the same computer. That’s a common configuration, but not the only one. If your web server is on a different computer, then change the localhost in xdebug.remote_host=localhost to the IP address of the computer on which NetBeans is running.
Tailored Installation Instructions
This page helps you finding which file to download, and how to configure PHP to get Xdebug running. Please paste the full output of phpinfo() (either a copy & paste of the HTML version, the HTML source or php -i output) and submit the form to receive tailored download and installation instructions. Do not paste the raw HTML (from view-source) into the form.