SMTP problem ( same as codeigniter 3)

oh, GOD.

app/Config/Autoload.php 
property $psr4
add a pair (namespace => path)

PHP Code:

'PHPMailer\PHPMailer' => APPPATH . 'ThirdParty/phpmailer/src' 


In a controller

PHP Code:

use PHPMailer\PHPMailer\PHPMailer

$mailer = new PHPMailer(); 


I dont want autoload phpmailer but use or only where i want use why the class aren't round?