Require a coupon code to signup for a Free MemberPress Membership (does not work with ReadyLaunch templates)

require-free-membership-coupon-code.php

<?php
// CHANGE this array - should be a comma separated list of Membership ID's to apply the signup codes to
$GLOBALS['free_memberships_require_coupon'] = array(2734);

function make_coupon_mandatory_free_membership($errors) {
	if(!isset($_POST['mepr_coupon_code']) || trim($_POST['mepr_coupon_code']) == '' && in_array($_POST['mepr_product_id'], $GLOBALS['free_memberships_require_coupon'])) {
		$errors[] = 'Sorry, a coupon code is required.';
	}

	return $errors;
}
add_filter('mepr-validate-signup', 'make_coupon_mandatory_free_membership');

// Needed to show hidden coupon field on free memberships
function show_coupon_field_free_membership() {
	$is_free_membership = false;
	foreach($GLOBALS['free_memberships_require_coupon'] as $membership_id) {
		if(is_single($membership_id)) {
			$is_free_membership = true;
		}
	}

	if($is_free_membership):
		?>
		<script type="text/javascript">
			(function($) {
				$(document).ready(function() {
					// Not needed for free memberships as coupon field is hidden and no link to enable it
					// Uncomment for non-free memberships though
					// $('.mepr-signup-form .have-coupon-link').trigger('click');
					
					$('input[name="mepr_coupon_code"]').attr("type", "text");
					$('input[name="mepr_coupon_code"]').before('<label>Coupon Code (Required)*</label>');
				});
			})(jQuery);
		</script>
		<?php
	endif;
}
add_action('wp_footer', 'show_coupon_field_free_membership');