candy2
  -candy1
  -candy1
  -candy1
candy2
  -candy1
  -candy1
  -candy1



  $value= $_POST['value'];

        $test  = $wpdb->get_results( $wpdb->prepare("SELECT candy1, candy2
                                                       FROM sweet
                                                       WHERE candy2 = %s",$value));

$tree = array();

foreach ($filter as $key => $value){
    $tree[]= array($filter->candy2 => $filter->candy1);
}
echo json_encode(tree);