How to get top parent id from a child id using php? - php

Question

I am an amateur in PHP. I tried a lot of suggestions from here but I didn't get the result I need. I want to get the top parent id of a child. ex. For id=10 top parent is 8. This is the array I get from the database. Thanks in advance.
$events = mysqli_query($dbtmx,"SELECT * FROM tmetrix_events WHERE status='1'");
while($re=mysqli_fetch_assoc($events)){
$array[] = array('id'=>$re['id'],'parent_id'=>$re['parent_id']);
}
And the array I am receiving is
Array
(
[0] => Array
(
[id] => 5
[parent_id] => 0
)
[1] => Array
(
[id] => 6
[parent_id] => 5
)
[2] => Array
(
[id] => 7
[parent_id] => 5
)
[3] => Array
(
[id] => 8
[parent_id] => 0
)
[4] => Array
(
[id] => 9
[parent_id] => 8
)
[5] => Array
(
[id] => 10
[parent_id] => 9
)
)
Now I want to find the top parent or root parent id of the child.
I tried Steverst1 and AymDev's code. But I am getting the result.

Answer 1

You can create a recursive function which will run through all parents until it finds 0 which I assume means there is no parent:
function get_top_parent(int $id, array $list): ?array
{
// Find current item
$key = array_search($id, array_column($list, 'id'));
$item = $list[$key] ?? null;
// Check if item has parent
if (null !== $item && $item['parent_id'] !== 0) {
// recursive call
return get_top_parent($item['parent_id'], $list);
}
// No parent (or no item)
return $item;
}
Tested on 3v4l.org: https://3v4l.org/PPm3K

Answer 2

Assumption that 0 in parent_id means that it is the parent we are looking for. So get the id of it.
$child_id = 10;
$parent = 0;
while ($child_id != 0) {
foreach ($array as $key => $inner_arr) {
$id = $inner_arr['id'];
$parent_id = $inner_arr['parent_id'];
if($id === $child_id){
$child_id = $parent_id;
$parent = $id;
}
}
}
echo $parent; // 8
Demo