WordPress at a glance
function is not described

PHPMailer\PHPMailer

PHPMailer::sign() public WP 1.0

Set the public and private key files and password for S/MIME signing.

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

No Hooks.

Return

null. Nothing.

Usage

$PHPMailer = new PHPMailer();
$PHPMailer->sign( $cert_filename, $key_filename, $key_pass, $extracerts_filename );
$cert_filename(string) (required)
-
$key_filename(string) (required)
-
$key_pass(string) (required)
Password for private key
$extracerts_filename(string)
Optional path to chain certificate

Code of PHPMailer::sign() WP 5.7.2

<?php
public function sign($cert_filename, $key_filename, $key_pass, $extracerts_filename = '')
{
    $this->sign_cert_file = $cert_filename;
    $this->sign_key_file = $key_filename;
    $this->sign_key_pass = $key_pass;
    $this->sign_extracerts_file = $extracerts_filename;
}