PHP Object+Collections to JSON Using json_encode

Question

In PHP, I have a product object that contains a collection of attributes. json_encode produces this:

{"id":"123","name":"abc","attributes":{"attributes":[{"key":"sku","value":"xyz"}]}}

"attributes" listed twice is redundant. What's the best way of structuring object collections so that the json is clean?

class Product {

    public $id;
    public $name;
    public $attributes;

    public function __construct()
    {
        $this->attributes = new Attributes();
    }

    public function get($id)
    {
        $this->id = "123";
        $this->name = "abc";
        $attribute = new Attribute("sku", "xyz");
        $this->attributes->add($attribute);
    }
}

class Attributes
{
    public $attributes;

    public function __construct()
    {
        $this->attributes = array();
    }

    public function add($attribute)
    {
        array_push($this->attributes, $attribute);
    }
}

class Attribute
{
    public $key;
    public $value;

    public function __construct($key, $value)
    {
        $this->set($key, $value);
    }
}

Jon Hulka · Accepted Answer · 2012-08-22 18:22:11Z

1

I would just use an associative array.

class Product {
...
    public $attributes=array();
    ...
    public function get($id)
    {
        ...
        $this->attributes["sku"]="xyz";
        $this->attributes["foo"]="bar";
    }
}

json_encode() should produce something like this:

{"id":"123","name":"abc","attributes":{"sku":"xyz","foo":"bar"}}

OR using variable variables:

class Attributes
{
    public function add($key,$value)
    {
        $this->{$key}=$value;
    }
    public function drop($key)
    {
        unset($this->{$key});
    }
}

$a=new Attributes();
$a->add('sku','xyz');
$a->add('foo','bar');
echo json_encode($a).'<br>';
$a->drop('sku');
echo json_encode($a).'<br>';

Output:

{"sku":"xyz","foo":"bar"}
{"foo":"bar"}

edited Aug 22, 2012 at 18:22

answered Aug 22, 2012 at 6:58

Jon Hulka

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3 Comments

Matthew Over a year ago

This would work in this specific case. However, this is a simplified version of a bigger picture. Better for us to stay with objects/collections and figure out a custom json output.

Jon Hulka Over a year ago

It's hard to say without knowing your specific requirements. I've added a way to implement the Attributes class using variable variables. It isn't completely compatible with your Attributes class in that it won't allow multiple attributes with the same key.

Matthew Over a year ago

Digging deeper. The way json_encode encodes objects/collections by default is good. Attributes is our exception and this is a good solution until we upgrade to PHP 9.4.

user462356 · Accepted Answer · 2012-08-22 06:50:27Z

1

You can give your classes a custom json encoding format by implementing JsonSerializable.

In your case you'll just need to have Attributes implement that and give it a jsonSerialize method which returns $this->attributes.

answered Aug 22, 2012 at 6:50

user462356

1 Comment

Matthew Over a year ago

Good solution. However, only available on PHP 5.4 and we're on 5.3.

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