Get tree by recursion - laravel

Question

I have a flat array with each element containing an 'InstitutionId' and a 'ParentInstitutionId'. Each element will only have ONE parent, but may have multiple children. I know it need recursive solution, I am stuck and can't find way out.
Array
(
[0] => Array
(
[InstitutionId] => 17507
[InstitutionName] => abc
[ParentInstitutionId] => 60936
)
[1] => Array
(
[InstitutionId] => 41679
[InstitutionName] => abc
[ParentInstitutionId] => 55701
)
[2] => Array
(
[InstitutionId] => 55701
[InstitutionName] => abc
[ParentInstitutionId] =>
)
[3] => Array
(
[InstitutionId] => 60936
[InstitutionName] => abc
[ParentInstitutionId] => 128629
)
[4] => Array
(
[InstitutionId] => 71737
[InstitutionName] => abc
[ParentInstitutionId] => 17507
)
)
How can I make this a tree, children and there children should come under one array starting from root.

Answer 1

You can use the hasMany relationship feature to achieve that. Here is one example you can adapt:
1st - Declare your relationship in your model with a significant name of your choosing. Here we say that the Tree model (file that we're currently in) HAS MANY Tree objects (yes, has many itself).
2nd - Declare the recursive tree loading all immediate children.
Tree Model
class Tree extends Model {
public function tree_immediate_children() {
return $this->hasMany(Tree::class);
}
public function recursive_tree(){
return $this->tree_immediate_children()->with('recursive_tree');
}
}
3rd - Eager load the relationship and then filter by absolute parents only. This way you only get the children through the parents.
Returning the Tree with Children
return \App\Tree::with('recursive_tree')->get()->where('tree_id', null);
This is the migration I used to achieve the previous code.
Migration
public function up() {
Schema::create('trees', function (Blueprint $table) {
$table->increments('id');
$table->string('name');
$table->timestamps();
$table->integer('tree_id')->unsigned()->nullable(true);
$table->index(['tree_id']);
$table->foreign('tree_id')->references('id')->on('trees')->onDelete('cascade');
});
}
public function down() {
Schema::drop('trees');
}
Result
{
"trees": [
{
"id": 1,
"name": "Lauriane Denesik",
"created_at": "2016-07-25 13:55:34",
"updated_at": "2016-07-25 13:55:34",
"tree_id": null,
"recursive_tree": [
{
"id": 4,
"name": "Lea Terry",
"created_at": "2016-07-25 13:55:39",
"updated_at": "2016-07-25 13:55:39",
"tree_id": 1,
"recursive_tree": []
},
{
"id": 5,
"name": "Erna Jacobi",
"created_at": "2016-07-25 13:55:39",
"updated_at": "2016-07-25 13:55:39",
"tree_id": 1,
"recursive_tree": []
},
{
"id": 6,
"name": "Carmen Ferry",
"created_at": "2016-07-25 13:55:39",
"updated_at": "2016-07-25 13:55:39",
"tree_id": 1,
"recursive_tree": [
{
"id": 10,
"name": "Alford Yost",
"created_at": "2016-07-25 13:55:44",
"updated_at": "2016-07-25 13:55:44",
"tree_id": 6,
"recursive_tree": []
},
{
"id": 11,
"name": "Eusebio Padberg",
"created_at": "2016-07-25 13:55:44",
"updated_at": "2016-07-25 13:55:44",
"tree_id": 6,
"recursive_tree": []
},
{
"id": 12,
"name": "Abdullah Wunsch",
"created_at": "2016-07-25 13:55:44",
"updated_at": "2016-07-25 13:55:44",
"tree_id": 6,
"recursive_tree": []
}
]
}
]
},
{
"id": 2,
"name": "Cruz Dickens",
"created_at": "2016-07-25 13:55:34",
"updated_at": "2016-07-25 13:55:34",
"tree_id": null,
"recursive_tree": [
{
"id": 7,
"name": "Mr. Jesus Macejkovic DDS",
"created_at": "2016-07-25 13:55:42",
"updated_at": "2016-07-25 13:55:42",
"tree_id": 2,
"recursive_tree": []
},
{
"id": 8,
"name": "Tracy Jacobson PhD",
"created_at": "2016-07-25 13:55:42",
"updated_at": "2016-07-25 13:55:42",
"tree_id": 2,
"recursive_tree": []
},
{
"id": 9,
"name": "Prof. Uriel Goldner",
"created_at": "2016-07-25 13:55:42",
"updated_at": "2016-07-25 13:55:42",
"tree_id": 2,
"recursive_tree": []
}
]
},
{
"id": 3,
"name": "Sabryna Torp",
"created_at": "2016-07-25 13:55:34",
"updated_at": "2016-07-25 13:55:34",
"tree_id": null,
"recursive_tree": []
}
]
}

Answer 2

Since your tags include Laravel, I will give you a laravel solution:
$collection = collect($yourArray)->keyBy('InstitutionId');
$grouped = $collection->groupBy('ParentInstitutionId')
->map(function($children){
return $children->keyBy('InstitutionId');
})->all();
$array = $collection->all();
foreach ($array as $id => $item ){
if (isset($grouped[$id]))
$array[$id]['children'] = $grouped[$id];
}
foreach ($array as $id => $item ){
if ($item['ParentInstitutionId']) {
$parentId = $item['ParentInstitutionId'];
$array[$parentId]['children'][$id] = $item;
}
}
$tree = array_shift($array);