WordPress at a glance
function is not described

IXR_Server::getCapabilities() public WP 1.0

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

No Hooks.

Return

Null. Nothing.

Usage

$IXR_Server = new IXR_Server();
$IXR_Server->getCapabilities( $args );

Code of IXR_Server::getCapabilities() WP 5.5.1

<?php
function getCapabilities($args)
{
    return $this->capabilities;
}