refresh PHP page via onclick event

Hi, Sorry to look like stupid for some of you, but i'm still not able to link to link (<a> </a>) or to a button via onclick event) the refresh of my page. i've check META tag and also $PHP_SELF variable, but it does not work. here is what i would like to do. i have 1 PHP page on which i have 3 flags (3 images) if user click on 1 of these flags, $_SESSION['Localization'] is set up to flag language and the page must be refreshed. thanks a lot for some help or tutorials. Alain