Cachearium\CacheData::appendCallback PHP Method

    public function appendCallback(callable $callback)
    {
        $this->data[] = array('type' => self::CACHEDATA_TYPE_CALLBACK, 'data' => $callback);
        return $this;
    }

 public function testCallback()
 {
     $cache = Cachearium\Backend\CacheRAM::singleton();
     $ck1 = new CacheKey('callback', 1, 'sub');
     $ck2 = new CacheKey('callback', 2, 'sub');
     $cd1 = new CacheData($ck1, null);
     $cd2 = new CacheData($ck2, null);
     $cd2->appendCallback('callbackDataTester');
     $cd1->appendData('something');
     $cd1->appendRecursionData($cd2);
     $this->assertTrue($cache->storeData($cd2));
     $this->assertTrue($cache->storeData($cd1));
     $this->assertNotFalse($cache->getData($ck2));
     $this->assertNotFalse($cache->getData($ck1));
     $this->assertEquals('something' . CALLBACKDATATESTERVALUE, $cd1->stringify($cache));
 }