原理：
找出文件前3个字符
如果它们对应的ASCII 值分别是 239，187，191
则判断为bom头,去掉前3个字符.
代码实现如下：
$basedir = isset($_GET['dir']) ? $_GET['dir'] : ".";
$auto = 1;
$auto = isset($_GET['auto']) ? $_GET['auto'] : $auto; checkdir($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);
}