Adding a custom question to WooCommerce Checkout, Saving the answer to the Database, Retrieving the Answer on order Completion

woocommerce___checkout___functions.php

<?php

// WooCommerce Add Custom Checkout Fields 
add_filter( 'woocommerce_checkout_fields' , 'custom_override_checkout_fields' );
function custom_override_checkout_fields( $fields ) {

	// append to the billing questions
	// we output a 'header' with CSS:before
    	 $fields['billing']['custom_question_slug'] = array(
        	'type'      => 'text',
        	'name'		=> 'custom_question',
        	'label'     => __('Custom Question', 'woocommerce'),
    		'placeholder'   => _x('Custom Question', 'placeholder', 'woocommerce'),
    		'required'  => true,
    		'class'     => array('form-row-wide custom_question_header'),
    		'clear'     => true
     	);
     	return $fields;
}

//
// Save the order meta with hidden field value
//
add_action('woocommerce_checkout_update_order_meta', 'custom_question_order_meta');
function custom_question_order_meta( $order_id ) {
	if ($_POST['custom_question_slug']) update_post_meta( $order_id, 'custom_question_slug', esc_attr($_POST['custom_question_slug']));
}

//
// WooCommerce create Member Post on checkout
//
add_action( 'woocommerce_order_status_completed', 'generate_rsc_entry' );
function generate_rsc_entry($order_id) {

    global $wpdb;

    // Getting the order (object type)
    $order = wc_get_order( $order_id );

    // Getting order items
    $items = $order->get_items(); 
    $total_items_qty = 0;

    // Iterating through each item (here we do it on first only)
    $order_item_id='';
    foreach ( $items as $key => $item ) {
        $total_items_qty += $item["qty"];
        $order_item_id=$key;
    }

	// Here's how to get stuff out of the $order
   	$customer_id = $order->customer_user;
    	$company = $order->billing_company;

	// Here's how to get our custom information reliably 
	$custom_question = $wpdb->get_var(
	$wpdb->prepare('
	SELECT `meta_value`
	FROM `wp_postmeta`
	WHERE `post_id` = %d
	AND `meta_key` = %s
	',
	$order_id,
	'custom_question_slug'
	)
	);
	
	// Now we do something awesome! Like - make a custom post
	$post_arr = array(
		'post_title'   => $company,
		'post_content' => '',
		'post_type' => 'member_rsc',
		'post_status'  => 'publish',
		'post_author'  => get_current_user_id(),
		'meta_input'   => array(
			'rsc-phone' => $rsc_name,
			'rsc-name' =>  $rsc_phone,
			'member-id' => $customer_id,
		),
	);

	wp_insert_post( $post_arr );
		
}

?>