<?php
srand(time());

$choice = rand(1,100);

$urls = array(10=>'http://www.google.com', 100=>'http://www.hotmail.com');
print_r($urls);
$final_url='';

foreach($urls as $odds => $href)
  if ($choice <= $odds) $final_url = $href;  

echo $final_url;

?>