检查php文件中是否含有bom的函数

<?php 
/*检测并清除BOM*/ 
if(isset($_GET['dir'])){ 
$basedir=$_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($dirname); 
} 
} 
}//end while 
closedir($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, $rest); 
return "<font color=red>BOM found, automatically removed.</font>"; 
}else{ 
return ("<font color=red>BOM found.</font>"); 
} 
} 3water.com 
else return ("BOM Not Found."); 
}//end function 
function rewrite($filename, $data){ 
$filenum = fopen($filename, "w"); 
flock($filenum, LOCK_EX); 
fwrite($filenum, $data); 
fclose($filenum); 
}//end function 
?>