dependent.php

<?php

public function getCMSFields() {
   $fields = Parent::getCMSFields();
   $fields->addFieldToTab('Root.Compare Vehicles', new TextField('Title')); 
   $fields->addFieldToTab('Root.Compare Vehicles', LabelField::create('Model 1'));
   //ArrayList::create(Car::get()->toArray())->RemoveDuplicates('MakesName');
   $map = Car::get()->map('ID', 'MakesNiceName')->toArray();

   $makes = new DropdownField('MakesName', 'MakesName', $map);
   $makes->setEmptyString('(Select Makes Name)');
   $fields->addFieldToTab('Root.Compare Vehicles', $makes);
   $datesSource = function($val) { 
       $v = Car::get()->filter(array('MakesNiceName'=>$val))->column('ModelName');
           // return appropriate options array if the value is one.\
       $map = array();
       //$test = array();
       foreach ($v as $name=>$val)
       {    
              if(!in_array($val, $map)){
                     $map[] = $val->ModelName;
              }
       }    
           //$test = array_unique($map);
           return $map;

   };
       
   $model = DependentDropdownField::create('FieldThree', 'ModelName', $datesSource)->setDepends($makes);
   $fields->addFieldToTab('Root.Compare Vehicles', $model); 
   
   $yearSource = function($val) { 
       $va = Car::get()->filter(array('id'=>$val));
       $modelname = array();
      foreach ($va as $name=>$val)
       {    
            $modelname[] = $val->ModelName;
       }    
       $new = current($modelname);
       $va = Car::get()->filter(array('ModelName'=>$new));
                  foreach ($va as $name=>$val)
       {    
            $map[] = $val->Year;
       } 

           //$test = array_unique($map);
           return array_unique($map);

   };

   $year = DependentDropdownField::create('FieldTwo', 'Year', $yearSource)->setDepends($model);
   $fields->addFieldToTab('Root.Compare Vehicles', $year);