How to write a controller for validation of multipaged form?

I'm struggling with the proper organisation of a (MVC) Controller for my validation of a multipaged form. The problem is that I not only have to check whether the user input is existant at all, but I have to match it with different databases (depending on the field), too. I also need that database-data that results from the user-input for different view-options.

It's unclear for me where I should put that validation at all. I would like to put not too detailed things into the controller, but at the same time I don't like models using each other (without the controller).

Here's a basic example from a controller, the steps stand for different stages/pages of the form:

// GET VARIABLES FROM $_POST + $_GET
 private function make_environment()
 {
     // PUT ALL VARIABLES INTO ARRAY
     $vars = array();
     if(!empty($_GET)) { $values = array_merge($vars,$_GET); }    
     if(!empty($_POST)) { $values = array_merge($vars,$_POST); }
 
     // PUT ALLOWED VARIABLES INTO PROPERTY
     foreach($this->properties as $property)
     {
         if(isset($values[$property]))
         {
             $this->properties[$property] = htmlspecialchars(trim($values[$property]));
         }
     }
 
 }
 
 
 // HANDLE DATA
 
 
 // PRODUCES DATA FOR VIEW    
 private function set_data()
 {
     $data = '';
     // CHOOSE DATA-OBJECT AND DATA-HANDLER
     switch($this->properties['step'])
     {
         case 1:
             // DATA HANDLER
             $handler = new calendar($this->properties);
             $data['calendar'] = $handler->return_data();
             break;
 
         case 2:
             // DATA HANDLER
             $handler = new form($this->properties);
             $data['form'] = $handler->return_data();
             break;
     }
 
     return $data;
 }
 
 
 // CREATE OR UPDATE VIEW
 
 private function run_view($data)
 {
     new view('header','');
 
     switch($this->properties['step'])
     {
         default:
             new view('chooser','');
             break;
         case 1:
             new view('calendar',$data['calendar'],$this->properties);
             break;
 
         case 2:
             new view('form',$data['form'],$this->properties);
             break;
     }
 
     new view('footer','');
 }
 

At the moment the different 'handlers' (in set_data()) are querying the database, but prior to that I'd need a check whether the required fields have been submitted and whether those fields are valid (whether they exist in the database). I don't really know where to put that kind of validation. Propably in a separate model, but then I'd have to query the DB there and in the data-handler again. Maybe you got an idea ?!

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