去掉文件的bom头

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* 不能登入或者不能登出；

 * 验证码不能正常显示;

* 页顶出现一条空白；

 * 页顶出现错误警告； 

* 其它不正常的情况。

<?php set_time_limit(120);
if (isset($_GET['dir'])) {//设置文件目录
    $basedir = $_GET['dir'];
} else {
    $basedir = '.';//无参数默认路径
}
$auto = 1;
checkdir($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 ("bom is cleaned");
        } else {
            return ("");
        }
    } else
        return ("BOM Not Found.");
}
 
function rewrite($filename, $data) {
    $filenum = fopen($filename, "w");
    flock($filenum, LOCK_EX);
    fwrite($filenum, $data);
    fclose($filenum);
}