Efficient Database Queries ( PHP + PDO SQL) - php

Question

At the moment I have a database structure like so:
| id | name | parent_id
| 1 | Human Resources | 0
| 2 | Marketing | 0
| 3 | Operations | 0
| 4 | Design | 0
| 5 | Marketing Design| 4
| 6 | Graphic Design | 4
| 7 | Print Design | 4
| 8 | Human Personal | 1
| 9 | Food Ops | 3
As you can see these are the departments within the business and also sub departments.
A sub-departments parent_id is the id of the department
do, for example:
id: 4, name: Design, parent_id: 0
id: 7, Print Design, parent_id: 4
Print Design is a sub department of design
I have called everything from the database in one query and now I need them in this structure:
$depts = array(
"Human Resources" => array("Human Personal"),
"Marketing" => array(),
"Operations" => array("Food Ops"),
"Design" => array("Marketing Design", "Graphic Design", "Print Design"),
...
);
so far I have:
foreach ($results as $result) {
if ($result['parent_id'] == 0) {
$parentCategories_arr[array($result['id'] => $result['name'])];
} else {
$returnedResults_arr[$result['parent_id']] = array($result['name']);
}
}
However I completely think that I have missed the point. so my question:
How do I loop through all the contents of that results and add the parent categories into an array with their sub categories as an array?

Answer 1

Maybe there is an easier way, but it works : (hate to say that sentence) - try to make it better maybe
$mFinalArray = fixMyArray($results);
print_r($mFinalArray);
function fixMyArray($results){
// Create categories - parent_id == 0
foreach($results as $index => $result) // $index = 0|1|2|3|4|5|6|7|8|9
if($result['parent_id'] == 0) // $result['parent_id'] = current item parent_id
$mCategories[$result['name']] = $result['id']; // $mCategories['Human Resources'] = 1|2|3|4
// Insert each data to the right parent
foreach($results as $index => $result) // $index = 0|1|2|3|4|5|6|7|8
if($result['parent_id'] != 0)
foreach($mCategories as $subindex => $category) // $subindex = Human Resources | Marketing | Operations | Design
if($result['parent_id'] == $category) // $category = 0|1|2|3|4
$mFinalArray[$subindex][] = $result['name']; // ex. $mFinalArray['Human Resources'][] = Human Personal
return $mFinalArray;
}
*Last line has an extra [ ] $mFinalArray[$subindex][ ]= $result['name'] . That means append to array.
Output :
Array
(
[Design] => Array
(
[0] => Marketing Design
[1] => Graphic Design
[2] => Print Design
)
[Human Resources] => Array
(
[0] => Human Personal
)
[Operations] => Array
(
[0] => Food Ops
)
)