Email verification on registration using php Mailer not working

I am trying to send and email for verification of a registration for my website i keep getting this error and I don't know how to fix it. These errors:

Warning: require(./vendor/autoload.php): Failed to open stream: No such file or directory in C:\xampp\htdocs\BUDGETING_WEBSITE\includes\signup.inc.php on line 7

Fatal error: Uncaught Error: Failed opening required './vendor/autoload.php' (include_path='C:\xampp\php\PEAR') in C:\xampp\htdocs\BUDGETING_WEBSITE\includes\signup.inc.php:7 Stack trace: #0 {main} thrown in C:\xampp\htdocs\BUDGETING_WEBSITE\includes\signup.inc.php on line 7

I installed phpMailer using Composer through the terminal. This is my code:

use PHPMailer\PHPMailer\PHPMailer;
use PHPMailer\PHPMailer\SMTP;
use PHPMailer\PHPMailer\Exception;

//Load Composer's autoloader
require 'vendor/autoload.php';


function sendemail_verify($full_name,$email,$verify_token)
{
    $mail = new PHPMailer(true);
    $mail->isSMTP();                                                        //Send using SMTP
    $mail->Host       = 'smtp.gmail.com';                                   //Set the SMTP server to send through
    $mail->SMTPAuth   = true;                                               //Enable SMTP authentication