Loop through an array while adding a new key:value pair based on another value

Question

I have the following data inside an multi level arrarray

1: id: 41, parent: null, name: lucas
2: id: 52, parent: null, name: george
3: id 98: parent: 41, name: julian
...

I need to loop through this array and a 'childrens' key and value to the parent while summing +1 to this value every time i run over an entry that has 'parent' not set to null. How to achieve this?

1: id: 41, parent: null, name: lucas, children: 1

I tried this inside a foreach

foreach($post as $parsedPost) {
    if($parsedPost['parent'] > 0){
        $idChild = $parsedPost['id'];
        $idParent = $parsedPost['parent'];
        $post[$idParent]["childrens"]++;
    }
 }

Of course, it returns a notice because the index ['childrens'] does not exist. Also, it's adding the childrens:value to the first children and not to the parent. Why?

Sorry @Saurabh, its supposed to be $idParent, i translated the var names before posting and forgot this one. EDIT: Fixed — Lucas Rabello Simões
– Lucas Rabello Simões, Commented Aug 1, 2016 at 5:43
to get rid of the notice add if( !isset($post[$idParent]['childrens']) ) { $post[$idParent]['childrens']=0; } before the line containing increment . — olegsv
– olegsv, Commented Aug 1, 2016 at 5:54
Thank you @olegsv. Do you know if it's possible to do what i want? I don't understand why my code does not work. If I echo $idChild has $idParent as a parent works, why $post[$idParent]["children"]++ does not work? — Lucas Rabello Simões
– Lucas Rabello Simões, Commented Aug 1, 2016 at 6:03
I wrote an implementation for this in 2010: stackoverflow.com/questions/3261228/… — Bill Karwin
– Bill Karwin, Commented Aug 1, 2016 at 6:12

Saurabh · Accepted Answer · 2016-08-01 07:04:02Z

1

Hope this helps.

$post[] = ["id" => "41", "parent" => null, "name" => "lucas"];
$post[] = ["id" => "52", "parent" => null, "name" => "george"];
$post[] = ["id" => "98", "parent" => "41", "name" => "Julian"];

foreach ($post as $parsedPost)
{
    if ($parsedPost['parent'] > 0 && $parsedPost['parent'] != "")
    {
        $idChild = $parsedPost['id'];
        $idParent = $parsedPost['parent'];
        $parentKey = array_search($idParent,array_column($post,'id'));
        if(!isset($post[$parentKey]["childrens"]))
        {
            $post[$parentKey]["childrens"] = 0;
        }
        $post[$parentKey]["childrens"]++;
    }
}
print_r($post);

Output:

Array
(
    [0] => Array
        (
            [id] => 41
            [parent] => 
            [name] => lucas
            [childrens] => 1
        )

    [1] => Array
        (
            [id] => 52
            [parent] => 
            [name] => george
        )

    [2] => Array
        (
            [id] => 98
            [parent] => 41
            [name] => Julian
        )

)

edited Aug 1, 2016 at 7:04

answered Aug 1, 2016 at 6:06

Saurabh

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11 Comments

Lucas Rabello Simões Over a year ago

your code does work, thank you! But it's skipping 1 children for every entries that have a children. Do you know why?

Saurabh Over a year ago

I didn't get you can you explain in more detail?

Lucas Rabello Simões Over a year ago

Entry 1 on my database has 6 childrens and your script calculates 6 childrens. while Entry 2 on my database has 3 childrens and your script calculates 2 childrens. I am going nuts over this one :D Glad you are helping

Saurabh Over a year ago

I added 3 children for id 52 and it is showing me 3 children.

olegsv Over a year ago

@LucasRabelloSimões can you post SQL table here?

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