framework/base/Model.php
public function getActiveValidators($attribute = null)
    {
        $activeAttributes = $this->activeAttributes();
        if ($attribute !== null && !in_array($attribute, $activeAttributes, true)) {
            return [];
        }
        $scenario = $this->getScenario();
        $validators = [];
        foreach ($this->getValidators() as $validator) {
            if ($attribute === null) {
                $validatorAttributes = $validator->getValidationAttributes($activeAttributes);
                $attributeValid = !empty($validatorAttributes);
            } else {
                $attributeValid = in_array($attribute, $validator->getValidationAttributes($attribute), true);
            }
            if ($attributeValid && $validator->isActive($scenario)) {
                $validators[] = $validator;
            }
        }

        return $validators;
    }
public function getActiveValidators($attribute = null)
    {
        $activeAttributes = $this->activeAttributes();
        if ($attribute !== null && !in_array($attribute, $activeAttributes, true)) {
            return [];
        }
        $scenario = $this->getScenario();
        $validators = [];
        foreach ($this->getValidators() as $validator) {
            if ($attribute === null) {
                $validatorAttributes = $validator->getValidationAttributes($activeAttributes);
                $attributeValid = !empty($validatorAttributes);
            } else {
                $attributeValid = in_array($attribute, $validator->getValidationAttributes($attribute), true);
            }
            if ($attributeValid && $validator->isActive($scenario)) {
                $validators[] = $validator;
            }
        }

        return $validators;
    }
Returns the validators applicable to the current [[scenario]].
@param string $attribute the name of the attribute whose applicable validators should be returned.
If this is null, the validators for ALL attributes in the model will be returned.
@return \yii\validators\Validator[] the validators applicable to the current [[scenario]].