<?php

class User
{

    public $username = Property::create()
      ->setType('string')
      ->setMaxLength(20)
      ->setMinLength(4)
      ->setRegularExpression('/[A-Za-z0-9.-]+/')
      ->setFunctionSet(function($val){
        // check if given username already exists
      })
    ;

    public $password = Property::create()
      ->setType('string')
      ->setMinLength(8)
      ->setMaxLength(30)
      ->setFunctionSet(function($val){
        return sha1($val);
      })
    ;

    public $lastActivity = Property::create()
      ->setType('datetime')
      ->setValue(time())
    ;