Change default input() function behaviour. You may use this hook to perform addtional checks to user input.

function my_component_init(){
ossn_add_hook('ossn', 'input', 'my_component_hook');
function my_component_hook($hook, $type, $return){
//$return[input] Input contain the name of input
//$return[noencode] To enacode or not
//$return[default] Default data if empty input,
//$return[strip] strip spaces (trim) default is true,
//$return[data] Actual data
return $return;
ossn_register_callback('ossn', 'init', 'my_component_init');

Example of this use case

Input default input