Cannot send email in phpMailer with ReactJs as frontend application - php

Question

I intend to send an email to the user that registers their account with an account verification link, so in that way I can keep them logged in the session, therefore to achieve that, I'm using phpMailer as email configuration in PHP, and as for frontend I'm using React.
However, even though the code is fine, the setup is alright, I even set up an application password for my project (less secure apps have been entirely disabled, and I'm using Gmail), but the email doesn't send at all.
I am wondering what could be the problem, maybe it could be an issue I overlooked in the code, or something wrong with the setup in general? I will attach the code lines from both React and PHP so you can take a look, thank you in advance!
P.S. I made use of send_email function due to getting undefined variable $to_email, despite it being defined in signup.php, and replaced the email and app password with generic names to cover them.
React (the handleSubmit function)
const handleSignUpSubmit = (event) => {
event.preventDefault();
const register_account = {
first_name: first_name,
last_name: last_name,
company: company,
email: email,
phone_number: phone_number,
password: password,
confirm_password: confirm_password,
};
axios
.post("http://localhost/bachelor_exam/signup.php", register_account)
.then((response) => {
if (response.data) {
navigate("/emailconfirm");
}
})
signup.php (where the data starts to be inserted in database)
} else {
$q=$db->prepare("INSERT INTO users(user_id, first_name, last_name, company, email, phone_number, password, forgot_password, token, verified) VALUES(:user_id, :first_name, :last_name, :company, :email, :phone_number, :password, :forgot_password, :token, :verified)");
$q->bindValue(":user_id", null);
$q->bindValue(":first_name", $firstName);
$q->bindValue(":last_name", $lastName);
$q->bindValue(":company", $company);
$q->bindValue(":email", $email);
$q->bindValue(":phone_number", $phoneNumber);
$q->bindValue(":password", $passwordHash);
$q->bindValue(":forgot_password", $forgotPass);
$q->bindValue(":token", $token);
$q->bindValue(":verified", false);
$q->execute();
$id = $db->lastInsertId();
$to_email = $email;
$subject = "Nuub - Account Confirmation";
$message = "Welcome to Nuub, click on the following link to verify your account:
<a href='http://localhost/bachelor_exam/confirm_account.php?token=$token'>Confirm your account</a>";
require_once("./emailVerification/send_email.php");
send_email($to_email, $subject, $message);
$_SESSION["first_name"] = $firstName;
header("Content-type: application/json");
http_response_code(200);
echo json_encode($_SESSION["first_name"]);
exit();
}
}
the PHPMailer configuration
<?php
header("Access-Control-Allow-Origin: *");
header("Access-Control-Allow-Methods: POST, GET");
header("Access-Control-Allow-Headers: Content-Type, Authorization");
use PHPMailer\PHPMailer\PHPMailer;
use PHPMailer\PHPMailer\Exception;
function send_email($to_email, $subject, $message){
if($_SERVER["HTTP_REFERER"] === "http://localhost:3000/"){
require '../emailVerification/include/Exception.php';
require '../emailVerification/include/PHPMailer.php';
require '../emailVerification/include/SMTP.php';
$mail = new PHPMailer(true);
try {
$mail->SMTPOptions = array(
'ssl' => array(
'verify_peer' => false,
'verify_peer_name' => false,
'allow_self_signed' => true
)
);
//Server settings
$mail->SMTPDebug = false; // Enable verbose debug output
$mail->isSMTP(); // Send using SMTP
$mail->Host = 'smtp.gmail.com'; // Set the SMTP server to send
through
$mail->SMTPAuth = true; // Enable SMTP
authentication
$mail->Username = 'email#gmail.com'; // SMTP username
$mail->Password = 'app_password'; // SMTP password
// $mail->SMTPSecure = PHPMailer::ENCRYPTION_STARTTLS; // Enable TLS encryption;
`PHPMailer::ENCRYPTION_SMTPS` also accepted
$mail->SMTPSecure = 'ssl'; // Enable TLS encryption;
`PHPMailer::ENCRYPTION_SMTPS` also accepted
$mail->Port = 465;
// $mail->Port = 587; // TCP port to connect to
//Recipients
$mail->setFrom('email#gmail.com', 'Nuub');
$mail->addAddress($to_email, 'user'); // Add a recipient
// $mail->addAddress('ellen#example.com'); // Name is optional
// $mail->addReplyTo('DUMMY_EMAIL_HERE_XXXXXXXXXXXXXXXXXX', 'Information');
// $mail->addCC('cc#example.com');
// $mail->addBCC('bcc#example.com');
// Attachments
// $mail->addAttachment('/var/tmp/file.tar.gz'); // Add attachments
// $mail->addAttachment('/tmp/image.jpg', 'new.jpg'); // Optional name
// Content
// $mail->isHTML(true); // Set email format to HTML
$mail->Subject = $subject;
$mail->Body = $message;
$mail->isHTML(true);
// $mail->AltBody = 'This is the body in plain text for non-HTML mail clients';
$mail->send();
if(!$mail->send()){
echo json_encode("Mail not sent" . $mail->ErrorInfo);
} else {
echo json_encode("Email has been sent");
}
} catch (Exception $e) {
echo json_encode("Message could not be sent. Mailer Error: {$mail->ErrorInfo}");
}
}
}