utf-8 for attachment in PHPmailer - php

Question

I've got problem with attachment name, if there are polish language diacritical signs, it won't display those signs.
I added just below php mailer class $mail->CharSet = 'UTF-8'; and it works for email body text( without it I had the same problem), but not for attachments. Also I had a similar problem with user name, but solved it with utf8_decode() function. Unfortunately that function is not working with attachment's name in my case.
<?php
//Import PHPMailer classes into the global namespace
//These must be at the top of your script, not inside a function
use PHPMailer\PHPMailer\PHPMailer;
use PHPMailer\PHPMailer\SMTP;
use PHPMailer\PHPMailer\Exception;
//Load Composer's autoloader
require 'autoload.php';
//Create an instance; passing `true` enables exceptions
$mail = new PHPMailer(true);
//$mail->addCustomHeader('Content-Type', 'text/plain;charset=utf-8');
$mail->CharSet = 'UTF-8';
$mail->Encoding = 'base64';
$honeypot = $_POST['honey'];
$user_name = utf8_decode($_POST['name']);
$user_email = $_POST['email'];
$user_message = $_POST['message'];
$user_phone = $_POST['phone'];
$honeypot = trim($_POST["honey"]);
$max_size = 2 * 1024 * 1204; //2mb
$attachment = $_FILES['uploaded-file'];
if ($_SERVER["REQUEST_METHOD"] == "POST") {
if(!empty($honeypot)) {
echo "NO SPAM!";
exit;
} else {
$mail = new PHPMailer; //From email address and name
$mail->isMail();
//sender
$mail->From = $user_email;
$mail->FromName = $user_name;
//recipient
$mail->addAddress("jaroslaw.mor#gmail.com");
//mail subject
$mail->Subject = "Zapytanie ze strony www";
$mail->isHTML(true);
//body mail
$mail->Body = "Telefon:$user_phone<br><br>Treść wiadomośći:<br>$user_message";
$mail->AltBody = "Telefon:$user_phone\n$content";
//attachment
if(isset($attachment)) {
for ($i = 0; $i < count($_FILES['uploaded-file']['name']); $i++) {
if ($_FILES['uploaded-file']['error'][$i] !== UPLOAD_ERR_OK) continue;
$file_TmpName = $_FILES['uploaded-file']["tmp_name"][$i];
$file_name = utf8_decode( $_FILES['uploaded-file']["name"][$i]);
if ($_FILES['uploaded-file']['size'][$i] > $max_size) {
echo "file is too big";
die();
}
else{
move_uploaded_file($file_TmpName, "uploads/" . $file_name);
$mail-> AddAttachment("uploads/". $file_name);
}
}//for
}//isset
if(!$mail->send()) {
echo "Mailer Error: " . $mail->ErrorInfo;
exit();
}
else {
header("Location: sent.html");
exit();
}//if send else
}//honey else end
}//post end

Answer 1

You can try to add this code before attachment upload:
setlocale( LC_ALL, "pl_PL.UTF-8" );

Answer 2

Try force encoding for attachment:
$mail->AddAttachment("uploads/", $file_name, $mail::ENCODING_BASE64, PHPMailer::filenameToType($file_name).'; charset=utf-8');

Answer 3

I tried all methods from here - without a positive result. By the accident I opened PHPMailer.php and noticed that there are some options connected with charset encoding, changed settings there and now it works.
Thx all for clues.