<?php
class Project_Entity_Address extends Zf_Domain_Entity
{
    public $id;
    public $userId;
    public $street;
    public $city;
    public $state;
}

class Project_DataMapper_Address extends Zf_DataSource_Dao_Mapper
{
    protected $_map = array(
        'id'      => 'id',
        'user_id' => 'userId',
        'street'  => 'street',
        'city'    => 'city',
        'state'   => 'state'
    );

    public function findAllByUserId($userId)
    {
        $dao = new Project_Dao_Db_Address();
        $rows = $dao->findAllByUserId($userId);
        if (!$rows || 0 === count($rows)) {
            return false;
        }
        
        $addresses = array();
        foreach ($rows as $row) {
            $addresses = $this->map($row);
        }
        return $addresses;
    }
}

class Project_Model_Address
{
    public function getByUserId($userId)
    {
        $mapper = new Project_DataMapper_Address();
        $mapper->setEntity(new Project_Entity_Address());
        $rows = $mapper->findAllByUserId($userId);

        return $rows;
    }
}

Fatal error: Class 'Zf_Domain_Entity' not found on line 2