Making an autoresponder in php - php

Question

I have a website that has a contact form. And when someone uses it I receive the message. But I would like to set up an autoresponder to inform the person who contacted me that their message has been received etc.
Code:
<?php
$data = json_decode(file_get_contents('admin/data/contact.txt'));
include('includes/header.php');
if(isset($_REQUEST['name'])) {
$to = $settings->email;
$subject = 'Contact from Website';
$headers = "From: " . strip_tags($_REQUEST['email']) . "\r\n";
$headers .= "Reply-To: ". strip_tags($_REQUEST['email']) . "\r\n";
//$headers .= "CC: susan#example.com\r\n";
$headers .= "MIME-Version: 1.0\r\n";
$headers .= "Content-Type: text/html; charset=ISO-8859-1\r\n";
$message = "Hi, A message from contact form.";
$message .= "<br /><br /><br />Name: ".$_REQUEST['name'];
$message .= "<br />Email: ".$_REQUEST['email'];
$message .= "<br />Subject: ".$_REQUEST['subject'];
$message .= "<br />Message: ".$_REQUEST['message'];
mail($to, $subject, $message, $headers);
$msg = 'Your Message has been sent. Thank You.';
}
$btn = '<input type="submit" style="font-size: 14px; font-style: normal; height: auto; color: #fff; border-radius: 15px; border: none;" class="btn_new" value="SEND" />';
?>
How can I edit this code in order to set this up?
Thank you

Answer 1

....
....
$message .= "<br />Message: ".$_REQUEST['message'];
if(#mail($to, $subject, $message, $headers))
{
echo "Mail Sent Successfully";
//Send autoresponder email to $_REQUEST['email'];
//inform the person who contacted me that their message has been received etc.
}
else
{
echo "Mail Not Sent";
}