php中隐形字符65279（utf-8的BOM头）问题

//remove the utf-8 boms 
 //by magicbug at gmail dot com 
  
 if (isset($_GET['dir'])){ //config the basedir 
   $basedir=$_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); 
}