WordPress at a glance
function is not described

PHPMailer\PHPMailer

PHPMailer::isSMTP() public WP 1.0

Send messages using SMTP.

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

No Hooks.

Return

null. Nothing.

Usage

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

Code of PHPMailer::isSMTP() WP 5.7.2

<?php
public function isSMTP()
{
    $this->Mailer = 'smtp';
}