add class to form in contact form 7 in wordpress

add class to specific form in contact form 7 in wordpress:

[contact-form-7 id="1234" title="Contact form 1" html_id="contact-form-1234" html_class="form contact-form"]

add class to ALL form in contact form 7 in wordpress:

/* add class for form in contact form 7

  ================================================== */

add_filter( 'wpcf7_form_class_attr', 'your_custom_form_class_attr' );

function your_custom_form_class_attr( $class ) {

  $class .= ' form-open-close';

  return $class;

}