Making changes on a different property of recursive function - php

Question

I'm currently developing this code that traverse a hierarchical array which should compute the sub-total of a property called cur_compensation. My issue is that the changes I do is not getting save
private function computeSubTotal($hierarchy){
foreach($hierarchy["_children"] as $key => $value){
if(isset($value["_children"]))
{
static::computeSubTotal($value);
}
else{
foreach($hierarchy["_children"] as $employee){
$employee_cur_compensation = $employee["cur_compensation"] ?? 0;
if (!isset($hierarchy["cur_compensation"])) {
$hierarchy["cur_compensation"] = 0;
}
$hierarchy["cur_compensation"] += $employee_cur_compensation;
}
return $hierarchy;
}
}
return $hierarchy;
}
This is the function so what it does it goes to the deepest node, the deepest node is a value that does not have any _children which mean it doesn't have any sub department (the hierarchy is sorted that the sub department are always on top)
The issue I have, once it reaches the bottom it computes the cur_compensation by looping through the employees of that department and adding it on the department "cur_compensation" property.
The issue is that, it doesn't save any of my changes.
So the purpose of the function is to add up the 'cur_compensation' of each employee/sub-department.
For example ->
$rows = array(
array(
'name' => "Main",
'id' => 1,
'parent_id' => 0,
'cur_compensation' => 0,
'_children' => array(
array(
'name' => "Dept A",
'id' => 2,
'parent_id' => 1),
),
array(
'name' => "Dept B",
'id' => 3,
'parent_id' => 1,
'_children' => array(
array(
'name' => "Dept C",
'cur_compensation' => 30000,
'id' => 4,
'parent_id' => 3),
array(
'name' => "Employee C",
'cur_compensation' => 30000,
'id' => 7,
'parent_id' => 3
)
)),
array(
'name' => "Employee A",
'cur_compensation' => 20000,
'id' => 5,
'parent_id' => 1
),
array(
'name' => "Employee B",
'cur_compensation' => 30000,
'id' => 6,
'parent_id' => 1
)
)
)
);
The result I want to get would be:
$rows = array(
array(
'name' => "Main",
'id' => 1,
'parent_id' => 0,
'cur_compensation' => 120000,
'_children' => array(
array(
'name' => "Dept A",
'id' => 2,
'cur_compensation' => 0,
'parent_id' => 1),
),
array(
'name' => "Dept B",
'id' => 3,
'parent_id' => 1,
'cur_compensation' => 60000,
'_children' => array(
array(
'name' => "Dept C",
'cur_compensation' => 30000,
'id' => 4,
'parent_id' => 3),
array(
'name' => "Employee C",
'cur_compensation' => 30000,
'id' => 7,
'parent_id' => 3
)
)),
array(
'name' => "Employee A",
'cur_compensation' => 30000,
'id' => 5,
'parent_id' => 1
),
array(
'name' => "Employee B",
'cur_compensation' => 30000,
'id' => 6,
'parent_id' => 1
)
)
)
);
So you would notice that Main and Dept B got the cur_compensation based on the _children property

Answer 1

There's a few things to make note on here - so I'm going to add comments to your existing code, then provide an example of how you could change it.
(I've formatted the code in each case)
class Example {
// filler code so that we can call
public function process($array){
return $this->computeSubTotal($array);
}
private function computeSubTotal($hierarchy) {
// we're not checking whether "_children" property exists before looping on it
foreach ($hierarchy["_children"] as $key => $value) {
if (isset($value["_children"])) {
// we're calling the method, but not doing anything with the return value.
static::computeSubTotal($value);
// we can set the original array value instead which will provide a modified copy
// this can be resolved by uncommenting the line below
// $hierarchy["_children"][$key] = static::computeSubTotal($value);
// also note that if this "child" doesn't have any *grand*children
// then we won't get an updated value due to how this is structured
// to fix this, you could remove the else wrapping so that the code
// below runs always
} else {
// double looping - we're already looping this array
// this will cause the end value to increase exponentially
foreach ($hierarchy["_children"] as $employee) {
$employee_cur_compensation = $employee["cur_compensation"] ?? 0;
if (!isset($hierarchy["cur_compensation"])) {
$hierarchy["cur_compensation"] = 0;
}
$hierarchy["cur_compensation"] += $employee_cur_compensation;
}
// returning whole array inside the loop is not ideal
// we have already adjusted the main array
// comment out this return to prevent that from happening
return $hierarchy;
}
}
return $hierarchy;
}
}
$example = new Example;
// calling this on $rows won't give us anything back
// since $rows doesn't contain the property "_children"
$rows = $example->process($rows);
// in this case, you would want to process each array result
// only on this primary array
foreach($rows as $index => $value){
$rows[$index] = $example->process($value);
}
echo json_encode($rows, JSON_PRETTY_PRINT);
Taking those comments into account, you would end up with something like this:
private function computeSubTotal($hierarchy) {
// we're not checking whether "_children" property exists before looping on it
foreach ($hierarchy["_children"] as $key => $value) {
if (isset($value["_children"])) {
$hierarchy["_children"][$key] = static::computeSubTotal($value);
}
// double looping - we're already looping this array
// this will cause the end value to increase exponentially
foreach ($hierarchy["_children"] as $employee) {
$employee_cur_compensation = $employee["cur_compensation"] ?? 0;
if (!isset($hierarchy["cur_compensation"])) {
$hierarchy["cur_compensation"] = 0;
}
$hierarchy["cur_compensation"] += $employee_cur_compensation;
}
}
return $hierarchy;
}
That's closer but still, it's not quite correct due to the double looping.
I've made a simpler version that is hopefully easy to follow:
private function computeSubTotal($hierarchy) {
if (!isset($hierarchy["_children"])) {
return $hierarchy;
}
// define this outside the loop for clarity
if (!isset($hierarchy["cur_compensation"])) {
$hierarchy["cur_compensation"] = 0;
}
foreach ($hierarchy["_children"] as $key => $value) {
// don't need to check for "_children" property
// as it's now handled in this function
$updated = static::computeSubTotal($value);
// reference the $updated array to increment
// the "cur_compensation" field
$hierarchy["cur_compensation"] += $updated["cur_compensation"] ?? 0;
// update original array
$hierarchy["_children"][$key] = $updated;
}
return $hierarchy;
}
// call like
foreach ($rows as $index => $value) {
$rows[$index] = static::computeSubTotal($value);
}
You will still need to change how you're passing the $rows variable due to it now containing a "_children" property (as shown in the examples) - either pass each element or add additional logic in that function to handle that.

Answer 2

You need to pass the array as a reference.
https://www.php.net/manual/en/language.references.pass.php
PHP passes the array to the function as a pointer, but when you try to update the array, PHP first makes a full copy of the array and updates the copy instead of the original.
Change your function signature to the following and it should be good.
private function computeSubTotal(&$hierarchy){
P.S. You are calling computeSubTotal statically, but the function is not static itself.