WordPress at a glance
function is not described

PHPMailer\PHPMailer

PHPMailer::setSMTPInstance() public WP 1.0

Provide an instance to use for SMTP operations.

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

No Hooks.

Return

SMTP.

Usage

$PHPMailer = new PHPMailer();
$PHPMailer->setSMTPInstance( $smtp );
$smtp(SMTP) (required)
-

Code of PHPMailer::setSMTPInstance() WP 5.7.2

<?php
public function setSMTPInstance(SMTP $smtp)
{
    $this->smtp = $smtp;

    return $this->smtp;
}