PHP 版去bom头

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);
}