如何正确处理PHP中16进制转换导致的中文乱码情况

// 将中文字符转换为UTF-8编码的二进制数据
function utf8_str_to_bin($str){
    $arr = preg_split('/(?<!^)(?!$)/u', $str);
    $bin_str = '';
    foreach($arr as $val){
        $bin_str .= pack("H*", bin2hex(mb_convert_encoding($val, 'UTF-16', 'UTF-8')));
    }
    return $bin_str;
}

// 将UTF-8编码的二进制数据转换为中文字符
function bin_to_utf8_str($bin_str){
    $str = '';
    $length = strlen($bin_str);
    for($i = 0; $i < $length; $i++){
        if($bin_str[$i] === '' && $bin_str[$i + 1] === 'x'){
            $hex = substr($bin_str, $i + 2, 2);
            $str .= mb_convert_encoding(pack('H*', $hex), 'UTF-8', 'UTF-16');
            $i += 3;
        }else{
            $str .= $bin_str[$i];
        }
    }
    return $str;
}

// 示例
$chinese_str = "你好";
$bin_data = utf8_str_to_bin($chinese_str);
$hex_data = bin2hex($bin_data);

echo "原始中文字符：".$chinese_str."<br>";
echo "中文字符转二进制数据：".$bin_data."<br>";
echo "二进制数据转16进制数据：".$hex_data."<br>";

$bin_data_back = hex2bin($hex_data);
$chinese_str_back = bin_to_utf8_str($bin_data_back);

echo "还原中文字符：".$chinese_str_back;