Issue loading phpmailer 6.0 - php

Question

Having problem with upgrading phpMailer 5.xx to 6.0. Used several versions of phpmailer for years, no problems like this. I prefer to not use composer.
From upgrade guide "Alternatively, if you're not using composer, copy the contents of the PHPMailer folder into one of the include_path directories specified in your PHP configuration and load each one manually." I prefer to not modify the include_path file on a shared host.
I used the PHPMailerAutoload.php for my 5.xx versions
I used this from the 6.0 package:
"Upgrading from PHPMailer 5.2 to 6.0
If you're not using composer, you can still load the classes manually, depending on what you're using:
use PHPMailer\PHPMailer\PHPMailer;
use PHPMailer\PHPMailer\Exception;
require 'src/PHPMailer.php';
require 'src/SMTP.php';
No errors reported on these
$mail = new PHPMailer(true);
Fatal error: Uncaught Error: Class 'PHPMailer' not found in ///path to my code
Tried $mail = new \PHPMailer(true);
Tried lower case file names for PHPMailer.php and SMTP.php
Tried class.PHPMailer.php and class.SMTP.php; and with lowercase filenames

Answer 1

Look at the examples for reference - you need to either use a namespaced class or reference it absolutely, for example:
use PHPMailer\PHPMailer\PHPMailer;
$mail = new PHPMailer(true);
or
$mail = new PHPMailer\PHPMailer\PHPMailer(true);
As came to light in your github ticket for the same question, use statements only apply in the file in which they are defined (see docs), and so your split into two files (which you didn't mention initially) breaks it. You have them split like this; in the first file:
use PHPMailer\PHPMailer\PHPMailer;
require 'src/PHPMailer.php';
and in the second file:
$mail = new PHPMailer(true);
The use statements do not apply to the second file, so the class is indeed undefined, though the requires are still valid as they are global. You need to split it like this:
require 'src/PHPMailer.php';
and:
use PHPMailer\PHPMailer\PHPMailer;
$mail = new PHPMailer(true);
For further info on upgrading to 6.0, read the upgrade guide.