php简单防盗链实现方法

<?php
$ADMIN = array(
  'defaulturl'=> 'http://blog.qita.in/images/banner-header.gif',
  //盗链返回的地址
  'url_1'   => 'http://blog.qita.in/file',
  'url_2'   => 'http://blog.qita.in/file1',
);
$okaysites = array(
 'http://qita.in',
  'http://blog.qita.in', //白名单
  'http://blog.qita.in/1.html',
);
$reffer = $_SERVER['HTTP_REFERER'];
if ($reffer) {
  $yes = 0;
  while (list($domain, $subarray) = each($okaysites)) {
    if (ereg($subarray, "$reffer")) {
      $yes = 1;
    }
  }
  $theu = 'url_' . $_GET['site'];
  $file = $_GET['file'];
  if ($ADMIN[$theu] and $yes == 1) {
  header("Location: $ADMIN[$theu]/$file");
  } else {
    header("Location: $ADMIN[defaulturl]");
  }
} else {
  header("Location: $ADMIN[defaulturl]");
}
print_r($_SERVER['HTTP_REFERER']);
?>