Nested array. Third level is disappearing

Question 1

I have that array :

$a = array(
    "7" => array(
        "id" => 7,
        "parent" => 6
    ),
    "6" => array(
        "id" => 6,
        "parent" => 5
    ),
    "5" => array(
        "id" => 5,
        "parent" => 4
    ),
    "4" => array(
        "id" => 4,
        "parent" => 0
    ),
    "3" => array(
        "id" => 7,
        "parent" => 2
    ),
    "2" => array(
        "id" => 7,
        "parent" => 1
    ),
    "1" => array(
        "id" => 7,
        "parent" => 0
    )
);

the result that I want is that :

$a = array(
    "4" => array(
        "id" => 4,
        "parent" => 0,
        array(
            "5" => array(
                "id" => 5,
                "parent" => 4,
                array(
                    "6" => array(
                        "id" => 6,
                        "parent" => 5,
                        array(
                            "7" => array(
                                "id" => 7,
                                "parent" => 6
                            )
                        )
                    )
                )
            )
        )
    ),
    "2" => array(
        "id" => 7,
        "parent" => 1,
        array(
            "3" => array(
                "id" => 7,
                "parent" => 2
            )
        )
    ),
    "1" => array(
        "id" => 7,
        "parent" => 0
    )
);

the code that I use is this :

foreach($a as $v)
{
    if(isset($a[$v['PARENT']]))
    {
        $a[$v['PARENT']][$v['ID']] = $v;
        unset($a[$v['ID']]);
    }
}

and the problem that I have is that I get that result :

$a = array(
    "4" => array(
        "id" => 4,
        "parent" => 0,
        array(
            "5" => array(
                "id" => 5,
                "parent" => 4
            )
        )
    ),
    "2" => array(
        "id" => 7,
        "parent" => 1,
        array(
            "3" => array(
                "id" => 7,
                "parent" => 2
            )
        )
    ),
    "1" => array(
        "id" => 7,
        "parent" => 0
    )
);

instead of the need it result.

Question 2

To solve your problem you need to properly understand how variable referencing/aliasing in PHP works.

Look at the following example code, which does not look much different to yours but makes use of references in order to access any parent even it has already "moved":

# transform $flat into a tree:
foreach($flat as $id => &$value)
{
    # check if there is a parent
    if ($parentId = $value['parent'])
    {
        $flat[$parentId][0][$id] =& $value; # add child to parent
        unset($flat[$id]); # remove reference from topmost level
    }
}
unset($value); # remove iterator reference
print_r($flat); # your tree

$flat now contains all values from $flat - but reordered. Demo.

Question 3

You need to iterate over your results, adding a new entry to the output when you encounter a new team, or updating the points value when you find the same team again. This is most easily done by initially indexing the output by the team name, and then using array_values to re-index the array numerically:

$teams = array();
foreach ($results as $result) {
    $team = $result['team'];
    if (!isset($teams[$team])) {
        $teams[$team] = array('team' => $team, 'points' => $result['punti']);
    }
    else {
        $teams[$team]['points'] += $result['punti'];
    }
}
$teams = array_values($teams);
print_r($teams);

Output (for your sample data):

Array
(
    [0] => Array
        (
            [team] => Red Bull Racing
            [points] => 418
        )
    [1] => Array
        (
            [team] => Scuderia Ferrari
            [points] => 353
        )
    [2] => Array
        (
            [team] => Mercedes-AMG
            [points] => 516
        )
    [3] => Array
        (
            [team] => Racing Point F1
            [points] => 147
        )
    [4] => Array
        (
            [team] => Haas F1
            [points] => 127
        )
)

Demo on 3v4l.org

Question 4

You could use a helper array for the levels.

var array = [{ no: 1, name: "ELECTRONICS", depth: 0 }, { no: 2, name: "TELEVISIONS", depth: 1 }, { no: 3, name: "TUBE", depth: 2 }, { no: 4, name: "LCD", depth: 2 }, { no: 5, name: "PLASMA", depth: 2 }, { no: 6, name: "PORTABLE ELECTRONICS", depth: 1 }, { no: 7, name: "MP3 PLAYERS", depth: 2 }, { no: 8, name: "FLASH", depth: 3 }, { no: 9, name: "CD PLAYERS", depth: 2 }, { no: 10, name: "2 WAY RADIOS", depth: 2 }],
    result = [],
    levels = [{ children: result }];

array.forEach(function (o) {
    levels[o.depth].children = levels[o.depth].children || [];
    levels[o.depth].children.push(levels[o.depth + 1] = o);
});

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Question 5

You can use JSON.stringify to walk on the tree easily:

const ids = [];
JSON.stringify(data, (key, value) => {
  if (key === 'id') ids.push(value);
  return value;
});

Question 6

You can do it like this, do the calculation from the innermost of the array. Check the demo.

<?php
function f(&$array)
{
    foreach($array as $k => &$v)
    {
        if(is_array($v))
        {
            if(count($v) == count($v, 1))
            {
                unset($array[$k]);
                if($k == 'sum')
                {
                    $v =  array_sum($v);
                    $array[] = $v;

                }elseif($k == 'multiply'){
                    $v = array_product($v);
                    $array[] = $v;
                }else{

                    foreach($v as $vv)
                        $array[] = $vv;
                }
            }else
                f($v);
        }
    }
}

while(count($array) != count($array, 1))
{
    f($array);
}

print_r($array);

Note：

traverse array from outer to inner
traverse array from inner to outer

Nested array. Third level is disappearing

Answers

php,arrays,multidimensional-array