Yii2 custom AppActiveQuery class used to extend yii\db\ActiveQuery to provide a cache function for backwards-compatibility with Yii 1.1 CActiveRecord->cache.

AppActiveQuery.php

<?php
namespace common\models\db;

class AppActiveQuery extends \yii\db\ActiveQuery
{
    private $cacheDuration = null;
    private $functionName = '';
    private $q = null;
    
    /**
     * Use query caching for this ActiveQuery.
     * 
     * @param int|null $duration Seconds to cache; Use 0 to indicate that the cached data will never expire; NULL indicates No Cache.
     * @return \common\models\db\AppActiveQuery
     */
    public function cache($duration = null)
    {
        if(!is_null($duration) && $duration >= 0) {
            $this->cacheDuration = $duration;
        }
        return $this;
    }
    
    public function all($db = null)
    {
        return $this->run('all', null, $db);
    }
    
    public function one($db = null)
    {
        return $this->run('one', null, $db);
    }
    
    public function count($q = '*', $db = null)
    {
        return $this->run('count', $q, $db);
    }
    
    public function sum($q, $db = null)
    {
        return $this->run('sum', $q, $db);
    }
    
    public function max($q, $db = null)
    {
        return $this->run('max', $q, $db);
    }
    
    public function min($q, $db = null)
    {
        return $this->run('min', $q, $db);
    }
    
    public function average($q, $db = null)
    {
        return $this->run('average', $q, $db);
    }
    
    public function scalar($db = null)
    {
        return $this->run('scalar', null, $db);
    }
    
    public function column($db = null)
    {
        return $this->run('column', null, $db);
    }
    
    public function exists($db = null)
    {
        return $this->run('exists', null, $db);
    }
    
    protected function run($functionName, $q, $db = null)
    {
        $this->functionName = $functionName;
        $this->q = $q;
        if(is_null($db)) {
            $modelClassName = $this->modelClass;
            $db = $modelClassName::getDb();
        }
        if(!is_null($this->cacheDuration)) {
            return $db->cache(function(\yii\db\Connection $db) {
                $functionName = $this->functionName;
                if(!is_null($this->q)) {
                    return parent::$functionName($this->q, $db);
                }
                else {
                    return parent::$functionName($db);
                }
            }, $this->cacheDuration);
        }
        else {
            if(!is_null($this->q)) {
                return parent::$functionName($this->q, $db);
            }
            else {
                return parent::$functionName($db);
            }
        }        
    }

}