快速去除整站程序文件编码中的BOM方法

<?php  
    if (isset($_GET['dir'])){ //设置文件目次  
    $basedir=$_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, $rest);  
       return ("<font color=red>BOM found, automatically removed._<a 
href=http://host.fbi1.net>http://host.fbi1.net</a></font>");  
      } else {  
       return ("<font color=red>BOM found.</font>");  
      }  
    }  
    else return ("BOM Not Found.");  
    }  
    function rewrite ($filename, $data) {  
    $filenum = fopen($filename, "w");  
    flock($filenum, LOCK_EX);  
    fwrite($filenum, $data);  
    fclose($filenum);  
    }  
?>