PHP send mail with attach

mail.php

<?php

$notAllowedExt = array('exe','apk'); //Неприемлимые расширения
$maxFileSize = 100 * 1024 * 1024; //100 MB

// Получатель (измените на ваш e-mail адрес)
$strEmail = "from@from.ru";
$email = filter_var($_REQUEST['email'],FILTER_VALIDATE_EMAIL);
if($email!==FALSE) {
	$name = filter_var($_REQUEST['name'],FILTER_SANITIZE_STRING);
	$subject = filter_var($_REQUEST['subject'],FILTER_SANITIZE_STRING);
	$message = filter_var($_REQUEST['message'],FILTER_SANITIZE_STRING);
	$headers = array();
	$headers[] = "MIME-Version: 1.0";

	if (isset($_FILES['file'])) {
	    //проверяем размер и тип файла
	    $ext = end(explode('.', strtolower($_FILES['file']['name'])));
	    if (in_array($ext, $notAllowedExt)) {
	        die('false');
	    }
	    if ($maxFileSize < $_FILES['file']['size']) {
	        die('false');
	    }
	    if (is_uploaded_file($_FILES['file']['tmp_name'])) {

	    	$attachment = chunk_split(base64_encode(file_get_contents($_FILES['file']['tmp_name'])));
			$fileName = $_FILES['file']['name'];
			$boundary =md5(date('r', time())); 

			$headers[] = "Content-Type: multipart/mixed; boundary=\"_1_$boundary\"";

//For attach------------------------------------------
$message="This is a multi-part message in MIME format.

--_1_$boundary
Content-Type: multipart/alternative; boundary=\"_2_$boundary\"

--_2_$boundary
Content-Type: text/plain; charset=\"utf-8\"

$message

--_2_$boundary--
--_1_$boundary
Content-Type: application/octet-stream; name=\"$fileName\" 
Content-Transfer-Encoding: base64 
Content-Disposition: attachment 

$attachment
--_1_$boundary--";
//For attach------------------------------------------
	    }
	}
	else $headers[] = "Content-type: text/plain; charset=utf-8";

	$headers[] = "From: Mail robot <support@site.ru>";
	$headers[] = "Reply-To: sender <".$email.">";
	$headers[] = "Subject: ".$subject;
	$headers[] = "X-Mailer: PHP/".phpversion();
	mail($strEmail,$subject,$name.":\r\n".$email.":\r\n".$message, implode("\r\n", $headers));
	echo 'success';
}
else echo 'false';