Yii2 throws a ReflectionException after installing phpmailer, why?

Question

Yii

After installing phpmailer on yii2 using composer, the application stub started to give an error:
Help me figure it out.

Answer 1

So it is written that you do not have a class.
This means that the autoloader is not working somewhere, or the class (package, module.) has been removed from the vendor.