add_filter('job_bm_registration_errors', 'job_bm_registration_errors_29072019'); function job_bm_registration_errors_29072019($error, $post_data){ if(empty($post_data['custom_form_field'])){ $error->add( 'custom_form_field', __( '<strong>ERROR</strong>: Field is empty.', 'job-board-manager' ) ); } return $error; }