php anti hotlink code

<?php
/**
* http://blog.qita.in
*/
$ADMIN = array(
    &#39;defaulturl&#39;=> &#39;http://blog.qita.in/images/banner-header.gif&#39;,  //盗链返回的地址
    &#39;url_1&#39;     => &#39;http://blog.qita.in/file&#39;,
    &#39;url_2&#39;     => &#39;http://blog.qita.in/file1&#39;,
);
$okaysites = array(
  &#39;http://qita.in&#39;,
    &#39;http://blog.qita.in&#39;,  //白名单
    &#39;http://blog.qita.in/1.html&#39;,
);
$reffer = $_SERVER[&#39;HTTP_REFERER&#39;];
if ($reffer) {
    $yes = 0;
    while (list($domain, $subarray) = each($okaysites)) {
        if (ereg($subarray, "$reffer")) {
            $yes = 1;
        }
    }
    $theu = &#39;url_&#39; . $_GET[&#39;site&#39;];
  $file = $_GET[&#39;file&#39;];
    if ($ADMIN[$theu] and $yes == 1) {
    header("Location: $ADMIN[$theu]/$file");
    } else {
        header("Location: $ADMIN[defaulturl]");
    }
} else {
    header("Location: $ADMIN[defaulturl]");
}
print_r($_SERVER[&#39;HTTP_REFERER&#39;]);
?>