framework/caching/Cache.php
protected function getValues($keys)
    {
        $results = [];
        foreach ($keys as $key) {
            $results[$key] = $this->getValue($key);
        }

        return $results;
    }
protected function getValues($keys)
    {
        $results = [];
        foreach ($keys as $key) {
            $results[$key] = $this->getValue($key);
        }

        return $results;
    }
Retrieves multiple values from cache with the specified keys.
The default implementation calls [[getValue()]] multiple times to retrieve
the cached values one by one. If the underlying cache storage supports multiget,
this method should be overridden to exploit that feature.
@param array $keys a list of keys identifying the cached values
@return array a list of cached values indexed by the keys