Extracting hierachy structure into json - php

Question

i am having trouble getting my mysql table into json.
I have a table that show the hierachy of employees like that:
The table is a employee table with
id, firstname, lastname, parentid
So now I want to query through the data to extract it into a multi level json object to simulate show the employees with their supervisors.
I hope somebody can help me with it.

Answer 1

Assuming you've already taken data from the database, below solution will get you what you need.
The way to go about it is via recursion.
php sandbox online
<?php
function buildTree(array &$elements, $parentId = 0) {
$branch = array();
foreach ($elements as $element) {
if ($element['parentid'] == $parentId) {
// recursion:
$children = buildTree($elements, $element['id']);
if ($children) {
$element['children'] = $children;
}
$branch[$element['id']] = $element;
unset($elements[$element['id']]);
}
}
return $branch;
}
$rows = [
['id' => 1, 'firstname' => 'john1', 'lastname' => 'doe', 'parentid' => 0],
['id' => 2, 'firstname' => 'john2', 'lastname' => 'doe', 'parentid' => 1],
['id' => 3, 'firstname' => 'john3', 'lastname' => 'doe', 'parentid' => 1],
['id' => 4, 'firstname' => 'john4', 'lastname' => 'doe', 'parentid' => 0],
['id' => 5, 'firstname' => 'john5', 'lastname' => 'doe', 'parentid' => 3],
];
print_r(buildTree($rows));
and the resulting array:
Array
(
[1] => Array
(
[id] => 1
[firstname] => john1
[lastname] => doe
[parentid] => 0
[children] => Array
(
[2] => Array
(
[id] => 2
[firstname] => john2
[lastname] => doe
[parentid] => 1
)
[3] => Array
(
[id] => 3
[firstname] => john3
[lastname] => doe
[parentid] => 1
[children] => Array
(
[5] => Array
(
[id] => 5
[firstname] => john5
[lastname] => doe
[parentid] => 3
)
)
)
)
)
[4] => Array
(
[id] => 4
[firstname] => john4
[lastname] => doe
[parentid] => 0
)
)
After you json_encode the result, you will get:
{
"1": {
"id": 1,
"firstname": "john1",
"lastname": "doe",
"parentid": 0,
"children": {
"2": {
"id": 2,
"firstname": "john2",
"lastname": "doe",
"parentid": 1
},
"3": {
"id": 3,
"firstname": "john3",
"lastname": "doe",
"parentid": 1,
"children": {
"5": {
"id": 5,
"firstname": "john5",
"lastname": "doe",
"parentid": 3
}
}
}
}
},
"4": {
"id": 4,
"firstname": "john4",
"lastname": "doe",
"parentid": 0
}
}