Q:

Install and Configure XHProf

Problem
I'm trying to configure and use XHProf. I've managed to get it installed and running on my server but I get a blank page when I try to access localhost/xhprof_html
This is the general post I've been following:
http://www.grasmash.com/article/installing-xhprof-drupal#view
Set-Up
I'm running a fresh Ubuntu Server 13.04. Its inside an VirtualBox
(Server set-up)
I installed xhprof using:
 sudo pecl install -f xhprof

I then added the following lines to my php.ini.
extension=xhprof.so
xhprof.output_dir="/tmp/xhprof"

I then rebooted apache and tested that xhprof is running using php -m. It is.
I then moved xhprof_html from /usr/share/php/ to /var/www/
But when I open localhost/xhprof_html/index.php I get a blank white screen. 
I had something similar when I first installed drupal and the following command fixed it:
$ sudo chown -R www-data /var/www/drupal/

However I can't it to work this time.
What have I done wrong?

A:

Two things seemed to fix this.
Number One:
Don't move xhprof_html. This seems to break it. Instead leave it where it is, or make a symlink from /var/www/xhprof_html to /usr/share/php/xhprof_html.
Number 2
Make sure you're testing for it correctly. 
Test 1:
php -m

It might show up there.
But it sometimes doesn't. The other way to check is to add a php file with 
phpinfo();

to /var/www and run it. Search for xhprof and if you find it, it's running. I didn't try the second one and was only using drupal integration to test for it, which wasn't working, so I missed that it was working.

