Ok, so to add a new field to the booking form you can use the built-in filter. You can add this code at the bottom of your theme’s functions.php file.
function wprm_custom_captcha( $booking_fields ) {
// Add the new field to the booking form
$booking_fields[] = array(
'type' => 'text',
'label' => '2+2 = ?',
'name' => 'wprm_math',
'placeholder' => '',
'value' => '',
'required' => true
);
return $booking_fields;
}
add_filter('wprm_booking_form_fields', 'wprm_custom_captcha' );
You should now see a new field into the form.
Now we need to tell the form what should do with that field. Unfortunately as of yet, there isn’t a filter to adjust the validation process of the form so we’ll have to edit the plugin manually.
Open file includes/class-wprm-bookings.php of the plugin and locate line 341 which should be empty. And add this code
if (isset($_POST['wprm_math']) && $_POST['wprm_math'] !== '4' ) {
$errors->add( 'cheater2', __('Are you trying to cheat?','wprm'));
}
It simply verifies whether the submitted value for that field is 4.
Regards.