What is the right way to concatenate?

Question

Yii

<?php echo $modelAbout->customer_ . Yii::$app->language; ?>

Error : Getting unknown property: app\models\About::customer_
What is the right way to concatenate ?

Answer 1

echo $modelAbout->{'customer_' . Yii::$app->language};

Answer 2

So:

<?php echo $modelAbout->customer_Yii::$app->language; ?>