Recursive function to build multidimensional array from objects

Question

I'm currently trying to write a PHP script that returns data structured as JSON. Below you can see an example of the output I'm looking to achieve:

Array
(
    [0] => GameObject
        (
            [id] => 1
            [parent_id] => 0
            [title] => Parent Page
            [Rounds] => Array
                        (
                           [0] => RoundObject
                                (
                                    [id] => 2
                                    [parent_id] => 1
                                    [title] => Sub Page
                                    [actions] => Array
                                )
                            [1] => RoundObject
                                (
                                    [id] => 2
                                    [parent_id] => 1
                                    [title] => Sub Page
                                    [actions] => Array
                                                (
                                                    [0] => ActionObject
                                                        (
                                                            [id] => 3
                                                            [parent_id] => 1
                                                            [title] => Sub Sub Page
                                                        )
                                                    [0] => ActionObject
                                                        (
                                                            [id] => 3
                                                            [parent_id] => 1
                                                            [title] => Sub                           Sub Page
                                                        )
                                                )
                                )
                        )
        )
    [1] => GameObject
        (
            [id] => 4
            [parent_id] => 0
            [title] => Another Parent Page
        )
)

The recursive function is suppose to start of with a GameObject or an array of GameObjects. Then call 'getChildren()' on the GameObjects and place the result in GameObject['Rounds']. Afterwards do the same thing with the RoundObject(s): call 'getChildren()' of the RoundObject and place the result in RoundObject['actions'].

An object such as GameObject have multiple children, children > 0. I know how the recursive function works, however I don't know how to structure the data to match my output example.

ANY HELP IS APPRECIATED! After many hours of trying different solutions I've gone desperate :).

Need clarification? Leave a comment :D

EDIT: My code currently looks like the following:

$response = create_response_object($game, $entityManager);

function create_response_object($arg, $entityManager)
{
    if(is_object($arg))
    {
        if($arg instanceof IWithChildren)
        {
            //If it's an object and it implements IWithChildren -> get its children
            $arg->children = $arg->getChildren($entityManager);
        }
        else
        {
            //End of the line. $arg is an object but doesn't have any children
        }
    }

    //$arg is an array filled with objects
    if(is_array($arg))
    {
        //If it's an array, loop through its contents
        foreach ($arg as $a)
        {
            //$arg['child'] = create_response_object($a, $entityManager);
            return create_response_object($a, $entityManager);
        }
    }

    return $arg;
}

print_r($response);

This is what the function returns:

Game Object
(
    [id:Game:private] => 9
    [gamestate:Game:private] => 0
    [player1ID:Game:private] => 30
    [player2ID:Game:private] => 1
    [currentPlayer:Game:private] => 1
    [winnerID:Game:private] => 
    [errorCollector:Game:private] => 
    [entityManager:Game:private] => 
    [children] => Array
        (
            [0] => Round Object
                (
                    [id:Round:private] => 7
                    [winnerID:Round:private] => 
                    [gameID:Round:private] => 9
                    [roundNumber:Round:private] => 0
                )

            [1] => Round Object
                (
                    [id:Round:private] => 8
                    [winnerID:Round:private] => 
                    [gameID:Round:private] => 9
                    [roundNumber:Round:private] => 1
                )

        )

)

THE EXPECTED RESPONSE: The response above seems to start of great when it adds a property called children and the value an array with children of said object. However it never goes beyond RoundObject, I want the function to continue retrieving children. I presume it has to do with the recursion in my function...

Need to see your try

Karim Harazin
– Karim Harazin

2017-01-08 03:46:45 +00:00
Commented Jan 8, 2017 at 3:46 — Karim Harazin
– Karim Harazin, Commented Jan 8, 2017 at 3:46
I edited the post to include my try and result of my try.

Andreas Johansson
– Andreas Johansson

2017-01-08 13:30:25 +00:00
Commented Jan 8, 2017 at 13:30 — Andreas Johansson
– Andreas Johansson, Commented Jan 8, 2017 at 13:30

shudder · Accepted Answer · 2017-01-08 15:07:27Z

1

Iterating array shouldn't return from function, only push children into each object. I'm not sure how your code interacts, but maybe you'll get the idea with this example:

foreach ($arg as $a) {
    //since $a is an object pointer ther's no need to reasign (using reference)
    //$a will have its children after calling this function
    create_response_object($a, $entityManager);
}

It looks like object ask manager to find its own children (!?) I don't know where to start... nevermind

When "gathering" children each of them should be asked for its children too, so you'll need something like this (recursively):

//go to function as an array & iterate populating each child with its children
$arg->children = create_response_object($arg->getChildren($entityManager), $entityManager);

You will need another if/else to determine children property Rounds/Actions
The problem is recursive in the procedural way, but not from objects' point of view. Rethink your design. Please.

Tip: Build an aggregate of game objects (GameState.. or something). When asked for Response this aggregate will iterate and gather response data from each game object, Game obejct asked for its data will need to iterate through its children... and so on.

answered Jan 8, 2017 at 15:07

shudder

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2 Comments

Andreas Johansson Over a year ago

Thanks for the response! Could you elaborate on your tip? Right now I'm using Doctrine(ORM) for PHP. I've mapped out the tables from my database as plain old objects such as Game, Round, Turn etc. Each class has a function called getChildren(). Game.getChildren() will return an array with all related Rounds, aka Rounds where the row's GameID matches the Game object's ID. Regarding your tip, it's really what I'm trying to achieve now. Iterating through children I understand, however structuring the data for an echo call back to my client is where I fail.

shudder Over a year ago

@AndreasJohansson getChildren() method is wrong imo (broken encapsulation) - object knows its children internally, but its client shouldn't know about them, so its rather getData() with iteration inside. I think Doctrine utilizes some serializer to build pure data structure responses (I'd search for/ask another question). I don't know how it works though, I'm avoiding ORMs - I like to waste some time on something trivial (but stable), because it gives me time to think about more complicated stuff. More typing, but without getting stuck.

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