WordPress at a glance
function is not described

PHPMailer\PHPMailer

PHPMailer::smtpClose() public WP 1.0

Close the active SMTP session if one exists.

{} It's a method of the class: PHPMailer{}

No Hooks.

Return

null. Nothing.

Usage

$PHPMailer = new PHPMailer();
$PHPMailer->smtpClose();

Code of PHPMailer::smtpClose() WP 5.7.2

<?php
public function smtpClose()
{
    if ((null !== $this->smtp) && $this->smtp->connected()) {
        $this->smtp->quit();
        $this->smtp->close();
    }
}