批量去除BOM头

<?php
/**
 *去除所有文件BOM
 *author Caihong_tang
 *@created 2016-6-13 10:05:34
 */
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, $rest); 
      return ("<p color=red>BOM found, automatically removed.</p>"); 
    } 
    else { 
      return ("<p color=red>BOM found.</p>"); 
    } 
  } 
  else return ("<p>bom not found.</p>
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                        </a>
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                            <div class="">
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                        </div>
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                    </div>
                "); 
} 
function rewrite ($filename, $data) { 
  $filenum = fopen($filename, "w"); 
  flock($filenum, LOCK_EX); 
  fwrite($filenum, $data); 
  fclose($filenum); 
}