How to properly validate a field in yii2?

Question

Yii

Good day!
I have a form with a multiple choice of cities
. I added [] so that an array of id cities comes to my server, how to properly validate this array, if you simply specify cities, one value will come, otherwise yii swears that it cannot find such a field cities[].

,

I need that there was only type int and the field was not empty

Answer 1

['cities', function ($attribute, $params, $validator) {
  if(is_array($this->$attribute)) {
    if(empty($this->$attribute)) {
      $this->addError($attribute, 'The array shouldnt be empty');
    }
     foreach($this->$attribute as $item)  {
        if(!is_int($item)) { 
           $this->addError($attribute, 'The array contains not an integer values');
           break; 
        }
     }            
  }
}],

Answer 2

[
   ['cities', 'each', 'rule' => ['required']],
   ['cities', 'each', 'rule' => ['integer']],
]

https://github.com/yiisoft/yii2/blob/master/docs/g...
mustn't, show the form