Can't create phpmailer object instance from phpmailer composer

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PHP

Hi I am currently working on a project that has a forgot password system in it. I decided to use PHPMailer to send reset password email to the user and I installed it via Composer and it is now in the vendor folder. However, after implementing the sample codes, PHP throws an error:

Notice: Undefined variable: mail in /opt/lampp/htdocs/capstone-admin/process/loginFunctions.php on line 98

Fatal error: Uncaught Error: Call to a member function isSMTP() on null in /opt/lampp/htdocs/capstone-admin/process/loginFunctions.php:98 Stack trace: #0 {main} thrown in /opt/lampp/htdocs/capstone-admin/process/loginFunctions.php on line 98

Here is a portion of my code in the loginFunctions.php:

<?php 
    use PHPMailer\PHPMailer\PHPMailer;
    use PHPMailer\PHPMailer\SMTP;
    use PHPMailer\PHPMailer\Exception;

    require __DIR__. '/../vendor/autoload.php';
    $mail = new PHPMailer();
    $mail->isSMTP();
    $mail->SMTPAuth = true;
    $mail->SMTPSecure = 'ssl';
    // More codes ......
?>

And my directory structure is:

- assets
- helpers
- process
  - loginFunctions.php
- vendor
  - composer
  - phpmailer / phpmailer
  - autoload.php
- views
- .gitignore
- composer.json
- composer.lock
- index.php
- README.md

What I have tried:

I tried searching for common questions and watching youtube videos but still no luck unfortunately. Any help is appeciated!