See the original post I read here: http://www.boallen.com/random-numbers.html
And the discussion here: http://reddit.com/r/programming/info/6k4gz/comments

It's interesting that PHP on windows has such a fake random function - yeah, I know, no body is true random, but this one is too far away... Guys on reddit says rand() use OS provide rand function buy mt_rand() use PHP's own implementation. It's really a big securiy hole.

And just for fun I write the data visualization code for ruby rand(): (Use RMagick)

require 'rubygems'
require 'RMagick'

include Magick
SIZE=512

img = Image.new SIZE, SIZE
d = Draw.new
d.fill 'black'
1.upto(SIZE) do |x|
  1.upto(SIZE) do |y|
    d.point(x, y) if rand > 0.5
  end
end
d.draw img
img.write 'random.png'
exit

You can see the output:



And here's the output from PHP: