some changes in the form structure

materio_search_api.module

@@ -693,21 +693,27 @@ function materio_search_api_advanced_search_form($form, &$form_state){
 
   $form = array(
     'title' => array(
-      '#prefix' => "<h2>",
+      '#prefix' => "<h3>",
       '#markup' => t("Advanced Search"),
-      '#suffix' => "</h2>",
+      '#suffix' => "</h3>",
     )
   );
 
   $vocabularies = variable_get('advancedsearchvocs', array());
 
+  $form['slider'] = array(
+    '#type' => 'fieldset',
+    // '#title' => $voc->name,
+    '#tree' => true,
+  );
+
   foreach ($vocabularies as $vid) {
     $voc = taxonomy_vocabulary_load($vid);
     // dsm($voc, 'voc');
 
-    $form['voc-'.$vid] = array(
+    $form['slider']['voc-'.$vid] = array(
       '#type' => 'fieldset',
-      '#title' => $voc->name,
+      // '#title' => $voc->name,
       '#tree' => true,
     );
 
@@ -728,7 +734,7 @@ function materio_search_api_advanced_search_form($form, &$form_state){
         || !count($children))
        continue;
 
-      $form['tree-'.$term->tid] = array(
+      $form['slider']['voc-'.$vid]['tree-'.$term->tid] = array(
         '#type' => 'fieldset',
         // '#title' => $term->name,
         '#attributes' => array("class"=>array("treelevel1")),
@@ -736,7 +742,7 @@ function materio_search_api_advanced_search_form($form, &$form_state){
       );
 
       $placeholder = t("Select an option");
-      $form['tree-'.$term->tid]['children'] = array(
+      $form['slider']['voc-'.$vid]['tree-'.$term->tid]['children'] = array(
         '#type' => 'select',
         '#title' =>  $term->name,
         '#attributes' => array(
@@ -785,7 +791,7 @@ function materio_search_api_advanced_search_form($form, &$form_state){
           if(count($dflt_values2))
             $classes2[] = 'visible';
 
-          $form['tree-'.$term->tid]['tid-'.$child->tid] = array(
+          $form['slider']['voc-'.$vid]['tree-'.$term->tid]['tid-'.$child->tid] = array(
             '#type' => 'select',
             '#title' => $child->name,
             '#multiple' => true,
@@ -803,19 +809,19 @@ function materio_search_api_advanced_search_form($form, &$form_state){
         }
       }
       if(count($options)){
-        $form['tree-'.$term->tid]['children']['#options'] = $options;
+        $form['slider']['voc-'.$vid]['tree-'.$term->tid]['children']['#options'] = $options;
       }else{
-        unset($form['tree-'.$term->tid]);
+        unset($form['slider']['voc-'.$vid]['tree-'.$term->tid]);
       }
     }
 
   }
 
-  $form['show'] = array(
-    '#type' => 'submit',//'image_button',
-    // '#src' => drupal_get_path('module', 'materio_search_api') . '/images/search.png',
+  $form['slider']['show'] = array(
+    '#type' => 'image_button',
+    '#src' => drupal_get_path('module', 'materio_search_api') . '/images/search.png',
     '#value' => t('Find'),
-    '#attributes' => array("class"=>array("btn","btn-lg")),
+    // '#attributes' => array("class"=>array("btn","btn-lg")),
     '#prefix' => '<div class="submits">',
     '#suffix' => '</div>',
   );
@@ -834,14 +840,17 @@ function materio_search_api_advanced_search_form_validate($form, &$form_state){
 function materio_search_api_advanced_search_form_submit($form, &$form_state){
   dsm($form, 'form');
   dsm($form_state, 'form_state');
-  $fs_values = $form_state['values'];
+  $fs_values = $form_state['values']['slider'];
+  unset($fs_values['show']);
   dsm($fs_values, 'values');
 
-  foreach($fs_values as $tree => $values){
-    foreach ($values as $values => $selected) {
-      if(is_array($selected) && count($selected)){
-        foreach ($selected as $tid) {
-          $tids[] = $tid;
+  foreach($fs_values as $voc => $trees){
+    foreach($trees as $tree => $values){
+      foreach ($values as $values => $selected) {
+        if(is_array($selected) && count($selected)){
+          foreach ($selected as $tid) {
+            $tids[] = $tid;
+          }
         }
       }
     }