This hook is used to alter the output text by messages or chat. (User message output). Chat and messages have same hook.

<?php
function my_component_init(){
		ossn_add_hook('messages', 'message:smilify', 'my_component_hook');
		ossn_add_hook('chat', 'message:smilify', 'my_component_hook');
}
function my_component_hook($hook, $type, $text, $params){
		//$text contains the output text
		//$params['instance'] contains message item instance example from, to, message(text).
		error_log(print_r($params, true));
		return $text;
}
ossn_register_callback('ossn', 'init', 'my_component_init');

Example of the usage is OssnSmilies componnet replacing smilies codes to icons.