PHP OOP Class design

Question

Comming from Java I feel more comfortable using Objects and Classes rather than plain functions. The question is: I currently have a 'User' class, which offers me methods such as getting access level, changing profile, erasing notifications, etc. Each method uses a query to my db to pull out the info needed or update it. But in the constructor I get the basic info: id, email, name and lastname (which are the fields I use the most on every method).

Which design would you use: (Current)

class User{
   private $id;
   private $email;
   ...

   function __construct($id){
      //Connect to database
      ...
      $this->id=$id;
      $thid->name=$row['name'];
      ...

   }

   function getEmail(){
       return $this->email;
   }
  ...
}

Or:

class User{
   private $id;

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

   function getEmail(){
       //Connect to database using id
       return $row['email'];
   }
   ...
}

I feel that being just a couple of text fields the performance would not be improved by the second one, but I'm a begginer so I don't know.

Thanks in advance

Middle ground: Use the lazy (second) version but cache the result! — Kerrek SB
– Kerrek SB, Commented Jul 22, 2011 at 18:39

Zak · Accepted Answer · 2011-07-26 20:35:54Z

3

Do version 1 and cache the results of your db query into fields in your object. You don't want to go to the db every time over the lifespan of the object and in a web app an object's lifetime is only the single page request, so there is little chance of non-atomic data operation pollution.

Further, don't connect to the database in your constructor. Take the time to build a class factory to generate your classes. Honestly you can even write a very simple code generator to generate both the model class that stores all your data fields and the mapper class that goes to the db and builds your object from a table in under 100 lines of code.

If you have the extra time, learn and use a framework like zend or for just data, doctrine...

(FWIW, I think learning simple zend table stuff would net you a time savings)

class User{
 protected $_id;
 protected $_email;
 protected $_username;
 protected $_userFirstName;

 public function __construct(){
 }
 public function setId($id){
   $this->_id = $id;
   return $this;
 }
 public function setEmail($email)
 {
   $this->_email = $email;
 }
  // etc and getters too
}

public class UserMapper
{
  protected $_connection;
  public function __construct($connection){
    $this->_connection = $connection;
  }
  public loadUser($id){ 
    $select = $this->_connection->select(' * from Users')
                         ->where('id = ?', $id);
    $result = $select->fetchAll();
    //error checking here
    $user = new User();
    $user->setId($results[0]['id'])
         ->setEmail($results[0]['email'])
         ->setUsername($results[0]['username']);
    return $user;
  }
  public saveUser(User $user){
  }
}

edited Jul 26, 2011 at 20:35

answered Jul 22, 2011 at 18:41

Zak

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4 Comments

Riskz Over a year ago

Ok that's what I have so far. But I have other functions that get info from other databases, is it OK for those not to be stored on construction? (I know I won't use them every time). Regarding the connection. What I have now is a function 'connect' which returns me a db connection, and I use that for querying. You have any source or link where I can see an example of a class factory in php? I'll give a try to Zend

Zak Over a year ago

Is it possible to wrap the smaller calls up as smaller objects that get instantiated when needed? Then those smaller objects can be created by their own factory and be lazy loaded too. (So yes, but wrap other data in smaller models using same idea)

Riskz Over a year ago

Ok now I understand. Thanks for the example. But what is the main advantage of connecting to the db in a mapper instead of the constructor? The only difference I see is that I can use the same mapper to load a lot of users. right?

Zak Over a year ago

There are a few things.. Say you wanted to make a bunch of mappers.. They might have common functionality.. You could refactor it into a base class. Somebody (Zend) might have already made that base class for you... When you separate responsibilities, it makes your code easier to maintain..

Naftali · Accepted Answer · 2011-07-22 18:40:31Z

1

I would say get all the rows on construct so that you don't have to do a new query every time you want to get something from the database.

So in conclusion: go with option #1.

answered Jul 22, 2011 at 18:40

Naftali

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Comments

genesis · Accepted Answer · 2011-07-22 18:41:34Z

0

I would use first, get all necessary details you think you'll use on most pages.

Second version is practice because to query database everytime you need is bad practice

answered Jul 22, 2011 at 18:41

genesis

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Comments

Dan Simon · Accepted Answer · 2011-07-22 18:42:37Z

0

Unless you're going to be working with large numbers of these objects at once, the difference in memory usage is very small. However the difference of executing one query vs several will be much more noticeable, so you should definitely only use one query to retrieve all the data at once.

answered Jul 22, 2011 at 18:42

Dan Simon

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