/* Execute all registered plugins of a particular hook. */
function plugin_call_hook($type, $data=array()) {
	global $plugin_hooks;

	if (isset($plugin_hooks[$type])) {
		if ($type == 'PRE_TEMPLATE') {
			if (isset($plugin_hooks['POST_TEMPLATE'])) {
				// We only start the buffer if there is a need
				ob_start();
			}
		} elseif ($type == 'POST_TEMPLATE') {
			// Abort if plugins trigger this hook without the PRE_TEMPLATE
			if (!isset($plugin_hooks['PRE_TEMPLATE'])) {
				return null;
			}
			$data = ob_get_contents();
			ob_end_clean();
		}
		foreach ($plugin_hooks[$type] as $func) {
			$data = call_user_func($func, $data);
		}
	}
	return $data;
}

 	/* Call themed template. */
	if (defined('plugins')) {
		plugin_call_hook('PRE_TEMPLATE');
	}
	require($WWW_ROOT_DISK . fud_theme .'language.inc');	// Initialize theme's language helper functions.
	require($WWW_ROOT_DISK . fud_theme . $t .'.php');
	if (defined('plugins')) {
		$htmlData = plugin_call_hook('POST_TEMPLATE');
		if (isset($plugin_hooks['POST_TEMPLATE']) && !empty($htmlData)) {
			// We only send output if process was not aborted
			echo $htmlData;
		}
	}

<?php
plugin_add_hook('PRE_TEMPLATE',  'plugin_x_capture_output');
plugin_add_hook('POST_TEMPLATE', 'plugin_x_process_output');

function plugin_x_capture_output() {
	//Run some code if desired.
}

function plugin_x_process_output($data) {
	//$modified_data = Modify $data, add headers, footers, go mad...
	return $modified_data;
}
?>