PHPMailer script sending email twice when CC added - php

Question

I'm trying to send an email that has a attachment generated using dompdf to a list of recipients. Using array_shift() for taking the primary email and remove it from the array and use foreach for taking every other email as CC. When I'm adding CC, email is sent twice. If there is no CC, it will be sent only once. Even if CC is blank , it is sent twice. If I remove that line AddCC(), it will be sent only once.
Any idea or help I can seek?
require_once 'dompdf/autoload.inc.php';
require_once 'phpqrcode/qrlib.php';
require 'PHPMailer/src/Exception.php';
require 'PHPMailer/src/PHPMailer.php';
require 'PHPMailer/src/SMTP.php';
$mail = new PHPMailer(true);
$recipients = array() // array of emails to be sent
try {
ob_start();
include "pdf.php";
$htmldata = ob_get_clean();
$options = new Dompdf\Options();
$options->getChroot($_SERVER['DOCUMENT_ROOT']);
$options->setisRemoteEnabled(true);
$options->setIsHtml5ParserEnabled(true);
$options->setTempDir('temp'); // temp folder with write permission
$dompdf = new Dompdf\Dompdf($options);
$dompdf->loadHtml($htmldata);
$customPaper = array(0,0,600,600);
$dompdf->set_paper($customPaper);
QRcode::png($data, "qr.png", "L", 4, 4);
$dompdf->render();
$output = $dompdf->output();
//Server settings
$mail->SMTPDebug = 1; // Enable verbose debug output
$mail->isSMTP(); // Set mailer to use SMTP
$mail->Host = ''; // Specify main and backup SMTP servers
$mail->SMTPAuth = true; // Enable SMTP authentication
$mail->Username = ''; // SMTP username
$mail->Password = ''; // SMTP password
$mail->SMTPSecure = 'tls'; // Enable TLS encryption, `ssl` also accepted
$mail->Port = 587; // TCP port to connect to
$mail->setFrom('', '');
$mail->addAddress(array_shift($recipients)); // Add first email as the recipient and remove the email from array
$mail->addReplyTo('');
foreach($recipients as $ccEmail)
{
$mail->AddCC($ccEmail);
}
$mail->addStringAttachment($output, 'attachment.pdf');
$mail->isHTML(true); // Set email format to HTML
$mail->Subject = 'Subject'.rand();
$mail->Body = 'Content';
$mail->AltBody = 'content';
$mail->send();
echo 'Message has been sent';
} catch (Exception $e) {
echo "Message could not be sent. Mailer Error: {$mail->ErrorInfo}";
}