Answered Update Profile Validation

[[!ExtUserUpdateProfile]]
[[!UpdateProfile?
	&preHooks=`FullName`
	&excludeExtended=`email:required:email,login-updprof-btn,mediaFolder`
	&validate=`nospam:blank,
		username:required,
		firstName:required,
		lastName:required,
		screenName:required:minLength=^3^,
		email:required:email`
	&useExtended=`0`
]]
[[!SetUserPlaceholders]]

<label for="screenName">Screen Name [[!+error.screenName]]</label>
<input type="text" name="screenName" id="screenName" value="[[+screenName]]">

if ($submission) {
if (strlen($_POST['firstName']) < 1) {
      return "";
   }
if (strlen($_POST['lastName']) < 1) {
      return "";
   }
if (strlen($_POST['businessAddressCounty']) < 1) {
      return "";
   }
if (strlen($_POST['businessAddressPostcode']) < 1) {
      return "";
   }
    $modx->request->sanitizeRequest();
    $dirty = false;
    foreach ($fields as $key => $value) {
        if (isset($_POST[$key])) {
            if ($value !== $_POST[$key]) {
                $data->set($key, $_POST[$key]);
                $dirty = true;
            }
        }
    }

    if ($dirty) {
        $data->save();
    }
}

return '';

if (empty($_POST['firstName'])) {
      return "";
   }

if ( (! isset($_POST['firstName'])) || empty($_POST['firstName'])) {
      return "";
}

echo "POST: " . print_r($_POST, true);