gistfile1.php

public function change()
{
  $users = $this->table('users');
  $users->addColumn('first_name', 'string', array('limit' => 30))
    ->addColumn('last_name', 'string', array('limit' => 30))
    ->addColumn('created', 'datetime')
    ->addColumn('updated', 'datetime', array('null' => true))
    ->save();
}