Implements the filter form that redirects to the page with parametes. Empty parameters are emmited.

form_redirect.php

/**
 * Implements FORM_ID_submit.
 */
function custom_user_auto_ecole_mes_examens_form_submit($form, &$form_state) {
  if ($form_state['values']['op'] == t('Search')) {
    $query = array_intersect_key(
      $form_state['values']['filters'],
      array_flip(
        array_filter(
          array_keys($form_state['values']['filters']),
          function ($var) use ($form_state) {
            return !empty($form_state['values']['filters'][$var]);
          }
        )
      )
    );

    $form_state['redirect'] = array(
      current_path(),
      array('query' => array('filters' => $query))
    );
  }
}