public function getInstalled()
{
if ($this->_installed === null) {
try {
$this->_installed = Yii::$app->db->createCommand("SHOW TABLES LIKE 'easyii_%'")->query()->count() > 0 ? true : false;
} catch (\Exception $e) {
$this->_installed = false;
}
}
return $this->_installed;
}