Temporary redirect prevents getting $_POST array

Question

I'm sending a form from a woocommerce plugin. I've tweaked the thankyou.php page and added email sending functionality. However the $_POST array is empty.

Inspecting with Chrome Dev Tools I found that there is temporary redirect from the posted page:

The relevant form code: (in /woocommerce/templates/checkout/form-checkout.php)

  <form enctype="multipart/form-data" name="checkout" method="post"  id="checky" class="checky" action="http://pharma-job.shared6.lighthost.co.il/checkout/order-received">
<input type="hidden" name="admin_email" value="<?php echo get_option('admin_email'); ?>" />
    <?php if ( sizeof( $woocommerce_checkout->checkout_fields ) > 0 ) : ?>

        <?php do_action( 'woocommerce_checkout_before_customer_details'); ?>

        <div class="col2-set" id="customer_details">

            <div class="col-1">

                <?php do_action('woocommerce_checkout_billing'); ?>

            </div>

            <div class="col-2">

                <?php do_action('woocommerce_checkout_shipping'); ?>

            </div>

        </div>
        <label for="cv_file">העלה קו"ח: </label>
  <input type="file" name="cv_file"> 
        <?php do_action( 'woocommerce_checkout_after_customer_details'); ?>

        <h3 id="order_review_heading"><?php _e('Your order', 'woocommerce'); ?></h3>

    <?php endif; ?>

    <?php do_action('woocommerce_checkout_order_review'); ?>

</form>

I looked at the generated HTML and found what appears to be the smoking gun:

<input type="hidden" name="_wp_http_referer" value="/checkout/" />

But what is the mechanism behind this redirect? How do I bypass it?

Answer 1

A brief background on the behavior of 3xx status codes

A 302 redirect is treated differently across browsers. Partially because of the variance of 302 in HTTP/1.0 and HTTP/1.1. HTTP 1.1 302 Found specifies that the request must not automatically be reprocessed at the returned location URI unless it can be confirmed by the user.

HTTP/1.0 were handled ambiguously prompting the creation of 303 and 307 for HTTP/1.1. 303 is to discard a POST where a 307 is to reprocess the request.

Data Flow

What is causing the redirect in this situation is unclear, but it is following a common behavior of resending the POST request as a GET request. I am assuming that all of the form processing is done elsewhere and sent to thankyou.php upon validation and a proper conversion. Based on this assumption there is likely a better place to tie in and implement the email functionality.