PHP检测并清除文件开头的BOM

网上看到的代码，收藏备份之，可以直接运行。

<?php
/*检测并清除BOM*/
$basedir = dirname(__FILE__);//扫描当前文件路径 可自动设置
$auto = 1;
checkdir($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($dirname);
				}
			}
		}//end while
	closedir($dh);
	}//end if($dh
}//end function
function checkBOM($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, $rest);
			return "<font color=red>BOM found, automatically removed.</font>";
		}else{
			return ("<font color=red>BOM found.</font>");
		}
	}
	else return ("BOM Not Found.");
}//end function
function rewrite($filename, $data){
	$filenum = fopen($filename, "w");
	flock($filenum, LOCK_EX);
	fwrite($filenum, $data);
	fclose($filenum);
}//end function