PHP去bom头

<?php
if (isset($_GET['dir'])){
$basedir=$_GET['dir'];
}else{
$basedir = '.';
}
$auto = 1;

checkdir($basedir);

function checkdir($basedir){
if ($dh = opendir($basedir)) {
   while (($file = readdir($dh)) !== false) {
    if ($file != '.' && $file != '..'){
     if (!is_dir($basedir."/".$file)) {
      echo "filename: $basedir/
$file ".checkBOM("$basedir/$file")." <br>";
     }else{
      $dirname = $basedir."/".
$file;
      checkdir($dirname);
     }
    }
   }
closedir($dh);
}
}

function checkBOM ($filename) {
global $auto;
$contents = file_get_contents($filename);
$charset[1] = substr($contents, 0, 1);
$charset[2] = substr($contents, 1, 1);
$charset[3] = substr($contents, 2, 1);
if (ord($charset[1]) == 239 && ord($charset[2]) == 187 &&
ord($charset[3]) == 191) {
   if ($auto == 1) {
    $rest = substr($contents, 3);
    rewrite ($filename, $rest);
    return ("<font color=red>BOM found,
automatically removed.</font>");
   } else {
    return ("<font color=red>BOM found.
</font>");
   }
}
else return ("BOM Not Found.");
}

function rewrite ($filename, $data) {
$filenum = fopen($filename, "w");
flock($filenum, LOCK_EX);
fwrite($filenum, $data);
fclose($filenum);
}
?>