PHP function to convert numbers mode

<?php
function changeNumbers($str,$mode='en',$mf='٫'){
 $latin=array('0','1','2','3','4','5','6','7','8','9','.');
 $farsi=array('۰','۱','۲','۳','۴','۵','۶','۷','۸','۹',$mf);
 return($mode=='fa')?str_replace($latin,$farsi,$str):str_replace($farsi,$latin,$str);
}
?>