How to create nested PHP array from simple multidimensional array

Question

I have a PHP array as follows

Array
(
    [1] => Array
        (
            [id] => 1
            [name] => Main Category
            [parent_id] => null
        )

    [2] => Array
        (
            [id] => 2
            [name] => sub category
            [parent_id] => 1
        )

    [3] => Array
        (
            [id] => 3
            [name] => child category
            [parent_id] => 2
        )

    [4] => Array
        (
            [id] => 4
            [name] => Main category 1
            [parent_id] => null
        )

    [5] => Array
        (
            [id] => 5
            [name] => sub category 1
            [parent_id] => 4
        )
    [6] => Array
        (
            [id] => 6
            [name] => child category 1
            [parent_id] => 5
        )

)

and I want this array to be converted as below using PHP

$categories = array(
    array(
        'id' => 1,
        'Name' => "Main Category",
        'sub' => array(
            id => 2,
            'Name' => 'Sub Category',
            'sub' => array(
                'id' => 3,
                'Name' => 'Child category',
                'sub' => 'None',
            )
        )
    ),
    array(
        'id' => 4,
        'Name' => "Main Category 1",
        'sub' => array(
            id => 5,
            'Name' => 'Sub Category 1',
            'sub' => array(
                'id' => 6,
                'Name' => 'Child category 1',
                'sub' => 'None',
            )
        )
    )
);

Actually I have a 3 level list hierarchy that looks something like this

A 1 level
 B 2 level under A
 C 2 level under A
   D level 3 under C

E 1 level
F 1 level 
  G 2 level under F

If provided information is not enough please ask me any question in comment. So the final output for my given example will look as below

Main category sub category child

Main category 1 sub category 2 child category 3

Here is what I tried.

foreach ($categoryList as $key => $value) {
            if ($value->getCategoryId()!=1) {
                $category[$key]['id'] = $value->getCategoryId();
                $category[$key]['name'] = $value->getName();
//                $category[$key]['parent_id'] = $value->getParentCategoryIds();
                $category[$key]['sub'] = $this->createSubCategoryArray($value->getCategoryId(), $categoryList);
            }
        }


 public function createSubCategoryArray($parentCatId, $categoryList)
        {
            foreach ($categoryList as $key => $category) {
                if($category->getCategoryId() == $parentCatId && $category->getCategoryId()!=1){
                    echo "string";
                    return array(
                        'id' => $category->getCategoryId(),
                        'name' => $category->getName(),
                        'sub' => $this->createSubCategoryArray($category->getCategoryId(), $categoryList)
                    );
                }
            }
        }

Answer 1

You can try something like this and can modify it as per your requirement

for($i=0;$i<count($arr);$i++){

    if( $arr[$i]['parent_id'] == null ){
        $data[] = array(
            'id' => $arr[$i]['id'],
            'Name' => $arr[$i]['name'],
            'sub' => array()
        );
    }elseif( $arr[$i]['parent_id'] != null){
        for($j=0;$j<count($data);$j++){
            if( $data[$j]['id'] == $arr[$i]['parent_id'] ){
                $data[$j]['sub'][] = createChild($arr[$i]); 
            }else{
                for($k=0;$k<count($data[$j]['sub']);$k++){
                    if($data[$j]['sub'][$k]['id'] == $arr[$i]['parent_id']){
                        $data[$j]['sub'][$k]['sub'] = createChild($arr[$i]);    
                    }
                }
            }
        }
    }
}

function createChild($obj){
    return array(
        'id' => $obj['id'],
        'name' => $obj['name'],
        'parent_id' => $obj['parent_id'],
        'sub' => array()
    );
}