Контактная форма PHP отправляет закодированный текст на тело письма

Контактная форма PHP отправляет закодированный текст на тело письма. Письмо содержит
вложение и текст из полей ввода. Сообщение должно быть декодировано до его отправки. Как я могу расшифровать "$message" с правильным текстом, который вводится?

Пожалуйста, посмотрите на код, указанный ниже:

if (isset($_POST['submit'])) {
if ($_POST['email'] == '' || $_FILES['file_upload'] == '' || $_POST["fname"] == '' || $_POST["lname"] == '' || $_POST["message"] == '') {
echo '<p class="red-info">Please Fill All The Fields</p>';

} else {

$from_email      = $_POST['email']; //from mail, it is mandatory with some hosts
$recipient_email = 'myemail@gmail.com'; //recipient email (most cases it is your personal email)

//Capture POST data from HTML form and Sanitize them,
$sender_fname   = filter_var($_POST["fname"], FILTER_SANITIZE_STRING); //sender name
$sender_lname   = filter_var($_POST["fname"], FILTER_SANITIZE_STRING); //sender name
$sender_phone_1 = filter_var($_POST["phone_1"], FILTER_SANITIZE_STRING); //sender name
$sender_phone_2 = filter_var($_POST["phone_2"], FILTER_SANITIZE_STRING); //sender name
$sender_phone_3 = filter_var($_POST["phone_3"], FILTER_SANITIZE_STRING); //sender name
$sender_phone   = $sender_phone_1 . ' ' . $sender_phone_2 . ' ' . $sender_phone_3; //sender name
$reply_to_email = filter_var($_POST["email"], FILTER_SANITIZE_STRING); //sender email used in "reply-to" header
$subject        = 'Contact Form'; //get subject from HTML form
$message        = filter_var($_POST["message"], FILTER_SANITIZE_STRING); //message

/* //don't forget to validate empty fields
if(strlen($sender_name)<1){
die('Name is too short or empty!');
}
*/

//Get uploaded file data
$file_tmp_name = $_FILES['file_upload']['tmp_name'];
$file_name     = $_FILES['file_upload']['name'];
$file_size     = $_FILES['file_upload']['size'];
$file_type     = $_FILES['file_upload']['type'];
$file_error    = $_FILES['file_upload']['error'];

if ($file_error > 0) {
die('Upload error or No files uploaded');
}
//read from the uploaded file & base64_encode content for the mail
$handle  = fopen($file_tmp_name, "r");
$content = fread($handle, $file_size);
fclose($handle);
$encoded_content = chunk_split(base64_encode($content));

$boundary = md5("sanwebe");
//header
$headers  = "MIME-Version: 1.0\r\n";
$headers .= "From:" . $from_email . "\r\n";
$headers .= "Reply-To: " . $reply_to_email . "" . "\r\n";
$headers .= "Content-Type: multipart/mixed; boundary = $boundary\r\n\r\n";

//plain text
$body = "--$boundary\r\n";
$body .= "Content-Type: text/plain; charset=ISO-8859-1\r\n";
$body .= "Content-Transfer-Encoding: base64\r\n\r\n";
$body .= "<br />First Name:" . $sender_fname;
$body .= "<br />Last Name:" . $sender_lname;
$body .= "<br />Phone:" . $sender_phone;
$body .= "<br />Message:";
$body .= chunk_split(base64_encode($message));

//attachment
$body .= "--$boundary\r\n";
$body .= "Content-Type: $file_type; name=" . $file_name . "\r\n";
$body .= "Content-Disposition: attachment; filename=" . $file_name . "\r\n";
$body .= "Content-Transfer-Encoding: base64\r\n";
$body .= "X-Attachment-Id: " . rand(1000, 99999) . "\r\n\r\n";
$body .= $encoded_content;

$sentMail = mail($recipient_email, $subject, $body, $headers);
if (isset($sentMail)) //output success or failure messages
{
echo '<p class="green-info">Your Email Has Been Submitted!We will contact soon.</p>';
echo "<script>document.contact.reset();</script>";
header("location: contect.php");
} else {
die('Could not send mail! Please check your PHP mail configuration.');
}
}

}