PHP, storing attributes.. Objects or values in array

Question

I'm just starting out with a new project which has a product class. An object will represent a product.

Each product has any number of un-defined attributes (could be colour, could be foobar etc..). The product object will contain an array of either attribute objects:

class attr {
  var type;  // string, float, int etc..
  var name;  // the name
  var value; // the value
  ...

(and then the product object has an array of these attr objects..)

OR should I store an array for each product:

class product {
  var attributes = array('colour' => 'red', 'weight' => '11')
  ...

Obviously I can make the array 2d and store the attribute type if I needed to.

My main concern is that products may have 20 or so attributes and with lots of users to the site I'm creating this could use up loads of memory - is that right, or just a myth?

I'm just wondering if someone knows what the best practice is for this sort of thing.. the object method feels more right but feels a bit wasteful to me. Any suggestions/thoughts?

20 or so attributes is a joke memory-wise. Start worrying once you get into the hundreds of thousands. Until then, code what makes the most sense. Do you get any advantage from making attributes individual objects? If yes, do it. If you properly encapsulate the attributes inside your class so only your class accesses them, you can change that scheme later at any time too. — deceze
– deceze ♦, Commented Dec 17, 2012 at 11:50
Yes, if they're objects it'll give far more flexibility later on.. thanks! :) — John Hunt
– John Hunt, Commented Dec 17, 2012 at 11:53
Having discussed with my colleagues, we are going to go the object route because we're not certain about anything! I guess that's the point. — John Hunt
– John Hunt, Commented Dec 17, 2012 at 12:33

deceze · Accepted Answer · 2012-12-17 12:04:59Z

2

As a general advise I'm against early optimization, especially if that means turning your OO models into implicit (non-modeled concepts) things like arrays. While I don't know what is the context in which you will be using them, having attributes as first class citizens will allow you to delegate behavior to them if you need, leading to a much cleaner design IMO. From my point of view you will mainly benefit in using the first approach if you need to manipulate the attributes, their types, etc.

Having said that, there are lots of frameworks that use the array approach for dynamically populating an object by using arrays and the _get()/_set() magic methods. You may want to take a look for example at how Elgg handles the $attributes array of the ElggEntity class to see it working and get some ideas.

HTH

edited Dec 17, 2012 at 12:04

deceze♦

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answered Dec 17, 2012 at 12:03

Andrés Fortier

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2 Comments

John Hunt Over a year ago

Although I think _get and _set are cool, I kind of get the feeling they are bad in some way.. eg it's too easy to 'break' your own rules. Still, interesting stuff - thanks!

Andrés Fortier Over a year ago

@JohnHunt: since PHP automatically defines a property when you assign a non-existent instance variable (e.g. $obj->non_existent_property=5), redefining __set() can actually help you to control that (e.g. by throwing an exception or logging it in your application). Also, consider that __get() and __set() can be used with the first (more OO) approach, pretty much for syntax sugar.

shadyyx · Accepted Answer · 2012-12-17 12:03:26Z

There is no best practice for that, AFAIK.

You have two options as described in Your question where each has its cos'n'pros. All it depends on is how/where the products and attributes will be stored - if it is in MySQL database still there shouldn't be a difference as You could fetch an array or an object from a DB.

If You are using classes for every simple thing, then use classes also for attributes, if You use classes only for the big objects, then use arrays. It is upon Your preference. There won't be any significant memory consumption difference when using classes or arrays and by no means while having 20 or so attributes.

If it was upon me, I'd go with classes and array of classes for attributes as it gives more advantages in the future should I need to extend the attributes some way.

Kevin · Accepted Answer · 2012-12-17 12:09:34Z

2

If the Product class really needs to be flexible and accomodate an arbitrary number of attributes, I would be tempted to make use of __get and __set e.g.

class Product {

    protected $attributes = array();

    public function __get($name) {

        if (array_key_exists($name, $this->attributes)) {
            return $this->attributes[$name];
        }
    }

    public function __set($name, $value) {

        $this->attributes[$name] = $value;
    }
}


$o = new Product();
$o->foo = 123;
var_dump($o->foo);

This would lend itself nicely to implementing ArrayAccess and other SPL iterator type classes in the future - if your solution required it.

answered Dec 17, 2012 at 12:09

Kevin

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Comments

Hugo Delsing · Accepted Answer · 2012-12-17 11:59:40Z

I thinks it more important to considering how you are going to store them in you database. I guess that you want to have a search where you could say something like I want a RED HAT size 12 then you must be able to find all the products that have attributes that match this. This is all done on a database level. It would not be a good idea to load all products in PHP classes first and then search.

Once you get what you want to show (search result, overview page, details) then you load the full product class with attributes. Since its all text/numbers and probably not more then a 100 products at once, speed wise it wont matter what you choose in PHP. Do what you like best.

In your database it could matter (since there you always works with all the products). Make sure you seperate strings/numbers/bools etc and put the correct indexes or you could have a mayor performance drop.

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