Why not come attached file to e-mail?

Hello! Why not come attachments (pictures) to the letter? The main data come type the name,email,phone ,etc., and the attached file there.

Are of the form:

<form action class="slider-form" id="formMain" method="post" name="formMain">
<input class="w100 border" id="nameFF" name="nameFF" placeholder="for example, Ivan Ivanovich Ivanov" required type="text" x-autocompletetype="name">
<input class="w100 border" id="contactFF" name="contactFF" placeholder="e.g. ivan@yandex.ru" required type="email" x-autocompletetype="email">
<label for="fileFF">Attach file:</label>
<input class="w100" id="fileFF" multiple="multiple" name="fileFF[]" type="file">
<input class="button-submit" id="button-post" type="button" value="Send">
</form>

Next is the type of Ajax:

$("#button-post").click(function () {
$.ajax({
 url: "/feedback/post.php",
 type: "POST",
 dataType: "html",
 data: jQuery("#"+formMain).serialize(), 
 success: function(response) {
 document.getElementById(result_id).innerHTML = response;
 }, 
 }); 

 }

Next php:

<?php
if (isset ($_POST['contactFF'])) {
 $to = "dadada@mail.ru"; // change to your email address
 $from = $_POST['contactFF'];
 $subject = "Completed contact form ".$_SERVER['HTTP_REFERER'];
 $message = "Name: ".$_POST['nameFF']."\nEmail: ".$"from"."\nIP: ".$_SERVER['REMOTE_ADDR'];
 $boundary = md5(date('r', time()));
 $filesize = ";
 $headers = "MIME-Version: 1.0\r\n";
 $headers .= "Content-Type: multipart/mixed; boundary=\"$boundary\"\r\n";
$message="
Content-Type: multipart/mixed; boundary=\"$boundary\"

--$boundary
Content-Type: text/plain; charset=\"utf-8\"
Content-Transfer-Encoding: 7bit

$message";
 for($i=0;$i<count($_FILES['fileFF']['name']);$i++) {
 if(is_uploaded_file($_FILES['fileFF']['tmp_name'][$i])) {
 $attachment = chunk_split(base64_encode(file_get_contents($_FILES['fileFF']['tmp_name'][$i])));
 $filename = $_FILES['fileFF']['name'][$i];
 $filetype = $_FILES['fileFF']['type'][$i];
 $filesize += $_FILES['fileFF']['size'][$i];
$message.="

--$boundary
Content-Type: \"$filetype\" name=\"$filename\"
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename=\"$filename\"

$attachment";
}
}
$message.="
--$boundary--";

 if ($filesize < 10000000) { // check for the total size of all files. Many mail services do not accept attachments larger than 10 MB
 mail($to, $subject, $message, $headers);
 echo $_POST['nameFF'].', Your message has been sent, thanks!';
 } else {
 echo 'Sorry, your email failed. The size of all files exceeds 10 MB.';
}
}
?>

What's wrong here? Why the attached file doesn't appear in the letter?
Thanks in advance.

PS can one example is. But there is a problem....I specifically did not use type="submit" because I have the visual editor is buggy))))Brad,but still...