examples/send_multiple_file_upload.phps

<?php

/**
 * PHPMailer multiple files upload and send example
 */

//Import the PHPMailer class into the global namespace
use PHPMailer\PHPMailer\PHPMailer;

require '../vendor/autoload.php';

$msg = '';
if (array_key_exists('userfile', $_FILES)) {
    //Create a message
    $mail = new PHPMailer();
    $mail->setFrom('from@example.com', 'First Last');
    $mail->addAddress('whoto@example.com', 'John Doe');
    $mail->Subject = 'PHPMailer file sender';
    $mail->Body = 'My message body';
    //Attach multiple files one by one
    for ($ct = 0, $ctMax = count($_FILES['userfile']['tmp_name']); $ct < $ctMax; $ct++) {
        //Extract an extension from the provided filename
        $ext = PHPMailer::mb_pathinfo($_FILES['userfile']['name'][$ct], PATHINFO_EXTENSION);
        //Define a safe location to move the uploaded file to, preserving the extension
        $uploadfile = tempnam(sys_get_temp_dir(), hash('sha256', $_FILES['userfile']['name'][$ct])) . '.' . $ext;
        $filename = $_FILES['userfile']['name'][$ct];
        if (move_uploaded_file($_FILES['userfile']['tmp_name'][$ct], $uploadfile)) {
            if (!$mail->addAttachment($uploadfile, $filename)) {
                $msg .= 'Failed to attach file ' . $filename;
            }
        } else {
            $msg .= 'Failed to move file to ' . $uploadfile;
        }
    }
    if (!$mail->send()) {
        $msg .= 'Mailer Error: ' . $mail->ErrorInfo;
    } else {
        $msg .= 'Message sent!';
    }
}
?>
<!DOCTYPE html>
<html lang="en">
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <title>PHPMailer Upload</title>
</head>
<body>
<?php if (empty($msg)) { ?>
    <form method="post" enctype="multipart/form-data">
        <input type="hidden" name="MAX_FILE_SIZE" value="100000">
        Select one or more files:
        <input name="userfile[]" type="file" multiple="multiple">
        <input type="submit" value="Send Files">
    </form>
<?php } else {
    echo htmlspecialchars($msg);
} ?>
</body>
</html>