Hooks for plugins

hi,

it would be nice to implements a "hook system" to allow plugin's developper to put an action before/after some standard action.
An example :

in phpmyvisites.php :
hook_before_new_visit($visitDatas);
... code to record new visit
hook_after_new_visit($visitDatas);

in my_plugin.php
register_hook_for("after_new_visit", "my_plugin_new_visit");


function my_plugin_new_visit($datas){
... what i want to do with the datas
}

So we can implement plugins without changing file phpmyvisites.php