PHP Form Submits But Does Not Display 1 Value - php

Question

I have a PHP form that works except for 1 thing and I am going nuts trying to figure out how to make it work. It emails me the results, and everything displays in the email fine except the "Plus1" field is always blank. How can I get the value to display in the submitted email form? Thanks for your help.
You can see it live on http://michyandsmiley.com.
Here is the code for the form:
<div id="rsvp" class="text-center" data-scroll-reveal>
<div class="heading">
<h2>RSVP</h2>
<p><span></span><i class="fa fa-heart"></i><span></span></p>
</div>
<form role="form" name="contactform" action="process.php">
<div class="row">
<div id="name-group" class="form-group col-xs-12">
<label for="inputName">Your Name</label>
<input type="text" class="form-control" id="inputName" name="inputName" placeholder="John Doe">
</div>
</div>
<div class="row">
<div id="email-group" class="form-group col-xs-12">
<label for="inputEmail">Your Email</label>
<input type="email" class="form-control" id="inputEmail" name="inputEmail" placeholder="name#domain.com">
</div>
</div>
<div class="row">
<div id="guests-group" class="form-group col-xs-6">
<label for="selectGuests">Total Guests</label>
<select class="form-control" name="selectGuests" id="selectGuests">
<option value="1" selected>1</option>
<option value="2">2</option>
</select>
</div>
<div id="plusone-group" class="form-group col-xs-6">
<label for="inputPlus1">Guest's Name</label>
<input type="Plus1" class="form-control" id="inputPlus1" name="inputPlus1" placeholder="Jane Doe">
</div>
<div class="row">
<div id="attending-group" class="form-group col-xs-12">
<label for="selectAttending">I am...</label>
<select class="form-control" name="selectAttending" id="selectAttending">
<option value="Attending" selected>So excited to attend! Yay!</option>
<option value="Not Attending">Sorry to miss it. Boo!</option>
</select>
</div>
</div>
<div class="row">
<button type="submit" class="btn btn-lg">Submit Your RSVP!</button>
</div>
</form>
</div>
And for the "process.php" code:
<?php
$send_to = '(removed my email for privacy purposes)';
$errors = array(); // array to hold validation errors
$data = array(); // array to pass back data
// validate the variables ======================================================
// if any of these variables don't exist, add an error to our $errors array
if (empty($_POST['inputName']))
$errors['name'] = 'Name is required.';
if (empty($_POST['inputEmail']))
$errors['email'] = 'Email is required.';
// return a response ===========================================================
// if there are any errors in our errors array, return a success boolean of false
if ( ! empty($errors)) {
// if there are items in our errors array, return those errors
$data['success'] = false;
$data['errors'] = $errors;
} else {
// if there are no errors process our form, then return a message
//If there is no errors, send the email
if( empty($errors) ) {
$subject = 'Wedding RSVP Form';
$headers = 'From: ' . $send_to . "\r\n" .
'Reply-To: ' . $send_to . "\r\n" .
'X-Mailer: PHP/' . phpversion();
$message = 'Name: ' . $_POST['inputName'] . '
Email: ' . $_POST['inputEmail'] . '
Guests: ' . $_POST['selectGuests'] . '
GuestName: ' . $_POST['inputPlus1'] . '
Attending: ' . $_POST['selectAttending'];
$headers = 'From: RSVP Form' . '<' . $send_to . '>' . "\r\n" . 'Reply-To: ' . $_POST['inputEmail'];
mail($send_to, $subject, $message, $headers);
}
// show a message of success and provide a true success variable
$data['success'] = true;
$data['message'] = 'Thank you!';
}
// return all our data to an AJAX call
echo json_encode($data);

Answer 1

You don't have the field in the field list to post to the server:
var formData = {
'inputName' : $('input[name=inputName]').val(),
'inputEmail' : $('input[name=inputEmail]').val(),
'selectGuests' : $('select[name=selectGuests]').val(),
'selectAttending' : $('select[name=selectAttending]').val()
};