Mail Send with Auto Reply Using Php

<?php
    if(isset($_POST['order_status_val']))
    {
        $to = 'xxx.xxxx@gmail.com';
        $too = $_POST['order_email'];
        $subject = 'Update Order Status';
$message = 'Order Id: '. strip_tags($_POST['order_id']);
        $message1 = 'Order Date Change to : '.strip_tags($_POST['pickup_date_ez']);

        $boundary =md5(date('r', time()));

        $headers = "From: info@xxxx.com";
        $headers .= "\r\nMIME-Version: 1.0\r\nContent-Type: multipart/mixed; boundary=\"_1_$boundary\"";
           $message2="We received your submission. We will contact you soon ...";                                                   
        $message="
$message\n$message1\n";
 mail($to, $subject, $message, $headers);
 @mail($too, $subject, $message2, $headers);
      echo '<script type="text/javascript">alert("Thank you! Your message has been sent.");</script>'; 
    }
?>
<form class="fild_sec_ordr" action="" method="post" id="customer_order_change">
<div class="input-group">
<input type="hidden" class="form-control" name="order_id" value="111111"/>
<input type="hidden" class="form-control" name="order_email" value="abc@gmail.com"/>
<select class="form-control" name="order_status_type">
<option value="">Choose Status</option>
<option value="Delivered">Delivered</option>
<option value="Completed">Completed</option>
<option value="Cancelled">Cancelled</option>
</select>
</div>
<div class="input-group btnsec">
<button type="submit" class="btn btnsubmit" name="customer_order_status">Submit</button>
</div>
</form>