hey all, this should be fairly easy to solve as i'm guessing this is a pretty basic question

i'm trying to check if a variable passed from a form is a valid address, containing letters, . or :
but php.net/preg_match doesn't help me much, somewhere between all the /\/// i get lost...

what i've scraped together is:
PHP Code:
 //letters, . and :
  
function isAddress($element) {
    return !
preg_match ("/something here/"$element);
  } 
it would be nice if you could help me out here, ir send me off to some tutorial i haven't found yet... cheers!