proper way to get all users using OOP

ive got a user class where i can get the name, date of birth etc of the user... (below)

class user {
    private $id;
    private $name;
    private $dob;
    private address;

    function __construct($id) {
         $this->id = $id
    }

}

i was just wondering what the best practice to get all users. do i create a function to 开发者_Go百科get an object of this class for each user found from the database? :s

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From a purely OO perspective, the User shouldn't have knowledge of databases etc.

My first thoughts would be a UserFactory, which will talk to the database and know how to build User objects from SQL results. You may want to specialise this to have a SQLUserFactory, an XMLUserFactory etc.

It's worth reading about Factory patterns. Factories look after the creation of objects. In this scenario, you may want to later distinguish between different types of User objects. In this scenario it would be the Factory's responsibility to decide what sort of object to create, not the User's.

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This looks like an attempt at Active Record. In php there are a few ORM implementations that include Active Record. I suggest looking into that.

Otherwise look into at PDO and binding query results to objects. You might be able to get something working that way.

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Do you mean which class should have the responsibility for getting Users from the DB?

The User class seems wrong, why would an indivudual user "know" about queries to obtain all (or some) users.

You could have a UserHome or UserKeeper class. and in there have methods which return result sets of user.

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Getting users from a database isn't an OOP question, it's a database question, and typically an SQL question. Unless I don't get what you mean?

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Object models in this case are somewhat artificial because putting a load() or get() method on the user class doesn't make a lot of sense because you don't want to get 100 users with 100 separate database roundtrips/selects. It's an example of "leaky abstractions". Implementation matters.

So you're going to need to write a function to run a query, return a bunch of rows and turn them into user objects.

Or use an ActiveRecord-like abstraction (eg that used in CodeIgniter or Kohana) to a set of records by passing in a criteria or a set of records.

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Assuming your users are stored in a MySQL database, I would create the following static method in Users. Well, I would probably use an ORM, like Doctrine instead, but...

static function queryAll() {
  $query = "SELECT id,name,dob,address FROM user";

  if ($result = $mysqli->query($query)) {
     $all = array();
     while ($obj = $result->fetch_object()) {
       $all[$obj->id] = $obj;
     }
     $result->close();
     return $all;
  }

  return array();

}

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In my point of view Database interaction should be separate and put in model as of in zend framework and controlled from controller where you should make of object of model class and call fetch all function.

Is this is the right approach.

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class User
{
    public $id;
    public $username;
    public $password;

    public function __construct()
    {
        $this->username = "";
        $this->password = "";

    }
}

separate database interactions to an interface

interface UserStore 
{
    public function Create(User $user) : User;
    //public function GetById(string $id) : ?User;
    public function getByUserName(string $userName) : ?User;
} 

implement the interface.

class MySqlUserStore implements UserStore
{
    public $db;

    public function __construct($db)
    {
        $this->db = $db;

    }

    public function Create( User $user) : User
    {
        $query = "INSERT INTO users (username, password) VALUES (?, ?)";
        $user->id = $this->db->insert($query, array($user->username, $user->password));
        return $user;
    }
    public function getByUserName(string $userName) : ?User
    {
        $query = "SELECT * from users where username = ?";
        $result = $this->db->select($query, array($userName));
        if(count($result) > 0) {
            $user = new User();
            $user->id = $result[0]['id'];
            $user->username = $result[0]['username'];
            $user->password = $result[0]['password'];
            return $user;
        }
        return null;

    }
} 

Use the user store

 $userStore = new MySqlUserStore($this->db);     
 $user = $userStore->getByUserName($username);