Random Image Forum Side Block?

[dsantana]

I'm looking for code that will go to a designated directory "/images/ads/sideblock" and grab like 4 or 5 images and place them randomly there.

I found this code and tried to use it as php on a sideblock but I got an error.
I'm not a codr so I though I'd ask you guys that are...
Any help would be awesome...
Thanks...

<?php
  // Configuration
  $image_path = "";
  $types = array(
    "GIF" => "image/gif",
    "JPG" => "image/jpg",
    "PNG" => "image/png");

  // Directory scan
  $file_list = array();
  $image_path = realpath(trim($image_path) != "" ? $image_path : ".") . "/";
  if ($image_path !== false && is_dir($image_path) && $handle = @opendir($image_path))
  {
    while (($file = readdir($handle)) !== false)
    {
      if (is_file($image_path . $file))
      {
        $file_extension = strtoupper(substr(strrchr($file, "."), 1));
        if (isset($types[$file_extension]))
        {
          $file_list[] = array(
            "filename" => $image_path . $file,
            "mimetype" => $types[$file_extension]);
        }
      }
    }
  }

  // Output
  if (sizeof($file_list) > 0)
  {
    shuffle($file_list);
    header("Content-Type: " . $file_list[0]["mimetype"]);
    header("Content-Length: " . @filesize($file_list[0]["filename"]));
    @readfile($file_list[0]["filename"]);
  }
  else
  {
    die("No images found.");
  }
?>