PHP批量去掉PHP文件中bom的代码

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