Finding Short Twitter Handles

shorthandles.php

<?php
  for ($i = 97; $i < 122; $i++) {
    for ($j = 0; $j < 100; $j++) {
      $usn = chr($i) . strval($j);
      $url="http://api.twitter.com/1/users/show.json?screen_name=".$usn;
      $json = file_get_contents($url,0,null,null);
      if ($http_response_header[0] == "HTTP/1.1 404 Not Found  ")
       echo "<p style='color:red'>$usn is available.</p>";
      else
       echo "<p style='color:grey'>$usn is not available.</p>  ";
    }
  }
?>