BOM character ufeff appears in PHP, PHP removes the weird BOM ufeff

When I was researching a PHP project, the project suddenly couldn’t be opened today.

It was fine a few days ago. I looked at the content of the Response using Chrome. There was a red dot in front of the content of the AJAX page and the ordinary HTML page.

Move the mouse up and it will prompt "ufeff".

Under Baidu, I found that it is a BOM character.

It was fine a few days ago. Is it because I replaced some content today?

I found a php program from the Internet, scanned all the files, and removed the BOM characters.

Damn it, why are there always so many different standards?

Code:

<?php
header('content-Type: text/html; charset=utf-8');
if(isset($_GET['dir'])){ //设置文件目录，如果没有设置，则自动设置为当前文件所在目录
    $basedir=$_GET['dir'];
}else{
    $basedir='.';
}
$auto=1;/*设置为1标示检测BOM并去除，设置为0标示只进行BOM检测，不去除*/

echo '当前查找的目录为：'.$basedir.'当前的设置是：';
echo $auto?'检测文件BOM同时去除检测到BOM文件的BOM<br />':'只检测文件BOM不执行去除BOM操作<br />';

checkdir($basedir);
function checkdir($basedir){
    if($dh=opendir($basedir)){
        while (($file=readdir($dh)) !== false){
            if($file != '.' && $file != '..'){
                if(!is_dir($basedir.'/'.$file)){
                    echo '文件: '.$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>找到BOM并已自动去除</font>');
        }else{
            return (' <font color=red>找到BOM</font>');
        }
    }else{
        return (' 没有找到BOM');
    }
}
function rewrite($filename,$data){
    $filenum=fopen($filename,'w');
    flock($filenum,LOCK_EX);
    fwrite($filenum,$data);
    fclose($filenum);
}
?>

Code from: http://www.douban.com/note/332229277/

The above introduces the occurrence of BOM character ufeff in PHP, and how to remove the weird BOM ufeff in PHP, including the relevant content. I hope it will be helpful to friends who are interested in PHP tutorials.