add_filter('wcfm_membership_registration_fields', function ($fields) {
    foreach(['first_name','last_name'] as $field_name) {
        if (isset($fields[$field_name])) {
            if (isset($fields[$field_name]['custom_attributes']) && is_array($fields[$field_name]['custom_attributes'])) {
                $fields[$field_name]['custom_attributes']['required'] = true;
            } else {
                $fields[$field_name]['custom_attributes'] = ['required' => true];
            }
        }
    }

    return $fields;
});

add_filter('wcfm_membership_registration_fields_address', function ($fields) {
    if (isset($fields['city'])) {
        if (isset($fields['city']['custom_attributes']) && is_array($fields['city']['custom_attributes'])) {
            $fields['city']['custom_attributes']['required'] = true;
        } else {
            $fields['city']['custom_attributes'] = ['required' => true];
        }
    }

    if (isset($fields['zip'])) {
        $fields['zip']['label'] = __('Postcode', 'wc-frontend-manager');
    }

    return $fields;
});

add_filter('wcfm_membership_registration_fields_phone', function ($fields) {
    if (isset($fields['phone'])) {
        $fields['phone']['label'] = __('Contact number', 'wc-frontend-manager');
    }

    return $fields;
});