vtxyzzy on "Can't get a WP query working"

I think this is what you want:

if ($_POST['plaats'] != '') {
   $meta_query = array(
      'relation' => 'OR',
      array(
         'key' => 'city',
         'value' => $_POST['plaats'],
         'compare' => 'LIKE'
      ),
      array(
         'key'     => 'city2',
         'value'   => $_POST['plaats'],
         'compare' => 'LIKE'
      )
   );
}