Use plugin hooks

/**
 * Return list of custom disp types handled by this plugin
 *
 * @return array list of disp modes handled by this plugin
 */
function GetHandledDispModes()
{
	return array(
			'disp_test', // display our test disp
		);
}


/**
 * Display our custom disp mode(s)
 *
 * @param mixed array $params
 * 		disp > display mode requested
 *
 * @return did we display?
 */
function HandleDispMode( $params )
{
	echo '<p>This is the test plugin handling the ['.$params['disp'].'] disp mode.</p>';
}