I have a them with a partial called 'contact' that loads a form.

The contact form looks like this:

<form name="sentMessage" id="contactForm" novalidate>
    <div class="row control-group">
        <div class="form-group col-xs-12 floating-label-form-group controls">
            <label>Name</label>
            <input type="text" class="form-control" placeholder="Name" id="name" required data-validation-required-message="Please enter your name.">
            <p class="help-block text-danger"></p>
        </div>
    </div>
    <div class="row control-group">
        <div class="form-group col-xs-12 floating-label-form-group controls">
            <label>Email Address</label>
            <input type="email" class="form-control" placeholder="Email Address" id="email" required data-validation-required-message="Please enter your email address.">
            <p class="help-block text-danger"></p>
        </div>
    </div>
    <div class="row control-group">
        <div class="form-group col-xs-12 floating-label-form-group controls">
            <label>Phone Number</label>
            <input type="tel" class="form-control" placeholder="Phone Number" id="phone" required data-validation-required-message="Please enter your phone number.">
            <p class="help-block text-danger"></p>
        </div>
    </div>
    <div class="row control-group">
        <div class="form-group col-xs-12 floating-label-form-group controls">
            <label>Message</label>
            <textarea rows="5" class="form-control" placeholder="Message" id="message" required data-validation-required-message="Please enter a message."></textarea>
            <p class="help-block text-danger"></p>
        </div>
    </div>
    <br>
    <div class="g-recaptcha" id="gcaptcha" data-sitekey="sitekeydataCjaelksjEJlakch"></div>
    <div id="success"></div>
    <div class="row">
        <div class="form-group col-xs-12">
            <button type="submit" class="btn btn-success btn-lg">Send</button>
        </div>
    </div>
</form>

There is JS on the front-end of this form that uses AJAX to submit the form to a PHP page (called contact_me.php) The JS looks like this:

$(function() {
    $("input,textarea").jqBootstrapValidation({
        preventSubmit: true,
        submitError: function($form, event, errors) {
            // additional error messages or events
        },
        submitSuccess: function($form, event) {
            event.preventDefault(); // prevent default submit behaviour
            // get values from FORM
            var name = $("input#name").val();
            var email = $("input#email").val();
            var phone = $("input#phone").val();
            var message = $("textarea#message").val();
            var gcaptcha = $("#gcaptcha").data('sitekey');

            var firstName = name; // For Success/Failure Message
            // Check for white space in name for Success/Fail message
            if (firstName.indexOf(' ') >= 0) {
                firstName = name.split(' ').slice(0, -1).join(' ');
            }
            $.ajax({
                url: "././mail/contact_me.php",
                type: "POST",
                data: {
                    name: name,
                    phone: phone,
                    email: email,
                    message: message,
                    gcaptcha: gcaptcha
                },
                cache: false,
                success: function() {
                    // Success message
                    $('#success').html("<div class='alert alert-success'>");
                    $('#success > .alert-success').html("<button type='button' class='close' data-dismiss='alert' aria-hidden='true'>&times;")
                        .append("</button>");
                    $('#success > .alert-success')
                        .append("<strong>Your message has been sent. </strong>");
                    $('#success > .alert-success')
                        .append('</div>');

                    //clear all fields
                    $('#contactForm').trigger("reset");
                },
                error: function() {
                    // Fail message
                    $('#success').html("<div class='alert alert-danger'>");
                    $('#success > .alert-danger').html("<button type='button' class='close' data-dismiss='alert' aria-hidden='true'>&times;")
                        .append("</button>");
                    $('#success > .alert-danger').append("<strong>Sorry " + firstName + ", it seems that my mail server is not responding. Please try again later!");
                    $('#success > .alert-danger').append('</div>');
                    //clear all fields
                    $('#contactForm').trigger("reset");
                },
            })
        },
        filter: function() {
            return $(this).is(":visible");
        },
    });

    $("a[data-toggle=\"tab\"]").click(function(e) {
        e.preventDefault();
        $(this).tab("show");
    });
});

Lastly - the PHP page. It looks like this:

<?php

// Check for empty fields
if(empty($_POST['name'])        ||
   empty($_POST['email'])       ||
   empty($_POST['phone'])       ||
   empty($_POST['message']) ||
   !filter_var($_POST['email'],FILTER_VALIDATE_EMAIL))
   {
    echo "No arguments Provided!";
    return false;
   }

$name = strip_tags(htmlspecialchars($_POST['name']));
$email_address = strip_tags(htmlspecialchars($_POST['email']));
$phone = strip_tags(htmlspecialchars($_POST['phone']));
$message = strip_tags(htmlspecialchars($_POST['message']));
$secret = "alkfejasupersecretkeyalkjeociyseh13987fa9s8df7";
$gcaptcha = $_POST['gcaptcha'];
$remoteip = $_SERVER['REMOTE_ADDR'];

$url = "https://www.google.com/recaptcha/api/siteverify?secret=".$secret."&response=".$gcaptcha."&remoteip=".$remoteip;
$result = json_decode($url, true);
var_dump($result);
/*
if ($result['success'] == 1) {
    //do mail here
}

// Create the email and send the message
$to = 'myemail@gmail.com'; // Add your email address inbetween the '' replacing yourname@yourdomain.com - This is where the form will send a message to.
$email_subject = "Website Contact Form:  $name";
$email_body = "You have received a new message from your website contact form.\n\n"."Here are the details:\n\nName: $name\n\nEmail: $email_address\n\nPhone: $phone\n\nMessage:\n$message";
$headers = "From: noreply@yourdomain.com\n"; // This is the email address the generated message will be from. We recommend using something like noreply@yourdomain.com.
$headers .= "Reply-To: $email_address";
mail($to,$email_subject,$email_body,$headers);
return true;
*/
?>

I just need something really simple - get a few inputs from users and use Google Recaptcha to help with spam, no biggie.

It looks like it works (I see the success message when I fill it all out) but then the data NEVER posts - there's never any var_dump or anything. Even when it was uncommented the mail never sent.

I need some help with this one!

This will do all that you need.

https://octobercms.com/plugin/martin-forms

Thanks for your input Sam. Normally I would say "hey, a plugin! Sounds good!", but I really wanted to do this to figure out how October process' this stuff more in depth.

I ended up figuring it out.

I got away from the JS $.ajax call all together and going a different route by adding the form processing on the default layout.

Got ya! I'm glad you got it figured out.

If you would really like to understand how forms work in october then I suggest having a look at this: https://octobercms.com/docs/markup/function-form

It may not be exactly what you're used to but once you understand it will be be much cleaner than the traditional way.