->validate()

$person = new DataObjects_Person;
$person->get(12);
$person->setFrom($_POST['input']);
$val = $person->validate();
if ($val === TRUE) {
  $person->update();
} else {
  foreach ($val as $k=>$v) {
    if ($v == false) {
      echo "There was something wrong with ($k)\n";
    } else {
      echo "($k) validated OK\n";
    }
  }
}

/* inside class DataObject_Person */
function validateEmail() {
  return Validate::email($this->email, true);
}

function validateHomepage() {
  return Validate::url($this->homepage, true);
}
function validateDate() {
  return Validate::date($this->date, "%d-%m-%Y", array(01,01,1970), array(01,01,2030));