cs/src/YiiConfig.php
public function mergeRules(array $rules)
    {
        $this->setRules(ArrayHelper::merge($this->getRules(), $rules));

        return $this;
    }
public function mergeRules(array $rules)
    {
        $this->setRules(ArrayHelper::merge($this->getRules(), $rules));

        return $this;
    }
Merge current rules config with provided list of rules.

@param array $rules
@return $this
@see setRules()
@see ArrayHelper::merge()