Add additional tab to CheckoutWC checkout flow for WooCommerce.

add-additional-tab.php

<?php
// Add to functions.php or with your favorite Code Snippets plugin
// Do not include opening PHP tag (<?php)

add_filter( 'cfw_get_checkout_tabs', 'add_age_verification_checkout_step' );

function add_age_verification_checkout_step( $tabs ) {
	/**
	 * Tab Priorities
	 * - Customer Info: 20
	 * - Shipping Method: 30
	 * - Payment Method: 40
	 */
	$tabs['age_verification'] = array(
		'label'            => 'Age Verification',
		'classes'          => array(),
		'priority'         => 25, // Between information and shipping method
		'enabled'          => true,
		'display_callback' => 'cfw_display_age_verification_checkout_step',
	);

	return $tabs;
}

function cfw_display_age_verification_checkout_step() {
	?>
	<h1>How old are you?</h1>
	<p>Listen kid, aren't you a bit young to be hanging out around here? Where are your parents?</p>

	<div class="cfw-bottom-controls">
		<div class="previous-button">
			<?php cfw_return_to_customer_information_link(); ?>
		</div>

		<?php cfw_continue_to_shipping_button(); ?>
	</div>
	<?php
}