WordPress at a glance
function is not described

PHPMailer\PHPMailer

PHPMailer::alternativeExists() public WP 1.0

Check if this message has an alternative body set.

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

No Hooks.

Return

true|false. Nothing.

Usage

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

Code of PHPMailer::alternativeExists() WP 5.7.2

<?php
public function alternativeExists()
{
    return !empty($this->AltBody);
}