How to include PHPmailer in functions.php properly (Wordpress) - php

Question

I'm trying to include PHPmailer in functions.php
my code:
add_action('wp_ajax_nopriv_test_mailer', 'test_mailer');
function test_mailer () {
try {
require_once(get_template_directory('/includes/mail/PHPMailer.php'));
require_once(get_template_directory('/includes/mail/Exception.php'));
$mail = new PHPMailer(true); // Passing `true` enables exceptions
//Server settings
$mail->SMTPDebug = 4; // Enable verbose debug output
$mail->isSMTP(); // Set mailer to use SMTP
$mail->Host = 'smtp.gmail.com';
$mail->SMTPAuth = true; // Enable SMTP authentication
$mail->Username = 'test#gmail.com'; // SMTP username
$mail->Password = 'dummypassword!'; // SMTP password
$mail->SMTPSecure = 'tls'; // Enable TLS encryption, `ssl` also accepted
$mail->Port = 587; // TCP port to connect to
//Recipients
$mail->setFrom('test#gmail.com', 'Mailer Test');
$mail->addAddress('john.doe#gmail.com', 'John User'); // Add a recipient
$mail->addReplyTo('test#gmail.com');
//Content
$mail->isHTML(true); // Set email format to HTML
$mail->Subject = 'Here is the subject testing';
$mail->Body = 'This is the HTML message body <b>in bold!</b>';
$mail->AltBody = 'This is the body in plain text for non-HTML mail clients';
$mail->send();
echo 'Message has been sent';
} catch (Exception $e) {
echo 'Message could not be sent. Mailer Error: ', $mail->ErrorInfo;
}
wp_die();
}
I also tried to put require_once out of the try catch still the same error here is the snippet about the error
"PHP Fatal error: Uncaught Error: Class 'PHPMailer' not found"
I use betheme template and I stored the files PHPmailer in betheme/includes/mail.

Answer 1

As BA_Webimax pointed out, you should be using Wordpress' built-in email functions, though due to WP's reliance on outdated PHP versions, you will end up using a very old version of PHPMailer with it.
Back to your current problem: It's not your require_once statements that are failing, it's that you have not imported the namespaced PHPMailer classes into your namespace. Add these at the top of your script:
use PHPMailer\PHPMailer\PHPMailer;
use PHPMailer\PHPMailer\Exception;
use PHPMailer\PHPMailer\SMTP;
Alternatively, use the FQCN when creating your instance:
$mail = new PHPMailer\PHPMailer\PHPMailer;
Note that this applies to the Exception class too, so you'd need to say:
catch (PHPMailer\PHPMailer\Exception $e) {

Answer 2

get_template_directory() returns the absolute path of the theme and doesn't take any params.
Try this for your includes:
require_once(get_template_directory().'/includes/mail/PHPMailer.php');
require_once(get_template_directory().'/includes/mail/Exception.php');