PHP/MySQL - Nested groups in JSON - php

Question

I'm creating nested (hierarchical) groups in JSON. The structure is simply - grand parent -> parent -> child:
main
secondary
mcondition
This is using the following MySQL/PHP to so far format main -> mcondition.
How should I change this to add the second level ('secondary' e.g. the parent level) between main and mcondition?
The column for secondary is mcondition.secondary
$query = 'SELECT * FROM mcondition ORDER BY mcondition.main ASC';
$result = $connection->query( $query );
$results = array();
$temp = array();
while ($line = mysqli_fetch_array($result)) {
$results[] = $line;
}
foreach($results as $row) {
$temp[$row['main']]['text'] = $row['main'];
if(!isset($temp[$row['main']]['children'])) {
$temp[$row['main']]['children'] = array();
}
array_push($temp[$row['main']]['children'], array(
'id' => $row['mcondition_pk'],
'text' => $row['mcondition_name']
));
}
$temp = array_values($temp);
echo json_encode($temp);
This is what the JSON currently looks like:
[
{
"text": "Main Heading 1",
"children": [
{
"id": "1",
"text": "mcondition_1"
},
{
"id": "17",
"text": "mcondition_4"
}
]
},
{
"text": "Main Heading 2",
"children": [
{
"id": "49",
"text": "mcondition_2"
},
{
"id": "48",
"text": "mcondition_5"
}
]
},
{
"text": "Main Heading 3",
"children": [
{
"id": "68",
"text": "mcondition_3"
},
{
"id": "67",
"text": "mcondition_6"
}
]
}
]
This is the structure of the table mcondition:
+---------------+------------+------+-----------+
| mcondition_pk | mcondition | main | secondary |
+---------------+------------+------+-----------+
Column mcondition is unique.

Answer 1

I'm still not 100% sure what your expected json would look like, but you should be able to do something like this. You may need to make some modifications to get exactly what you're wanting. I'm using an array $results to simulate the data acquisition from the database. This will get you a nested hierarchical structure.
$out = [];
$results = [
['main' => 'mk1', 'secondary' => 'sk1', 'mcondition_pk' => 1, 'mcondition' => 'mcondition_1'],
['main' => 'mk1', 'secondary' => 'sk2', 'mcondition_pk' => 2, 'mcondition' => 'mcondition_2'],
['main' => 'mk1', 'secondary' => 'sk2', 'mcondition_pk' => 3, 'mcondition' => 'mcondition_3'],
['main' => 'mk2', 'secondary' => 'sk3', 'mcondition_pk' => 4, 'mcondition' => 'mcondition_4'],
['main' => 'mk2', 'secondary' => 'sk3', 'mcondition_pk' => 5, 'mcondition' => 'mcondition_5'],
['main' => 'mk3', 'secondary' => 'sk4', 'mcondition_pk' => 6, 'mcondition' => 'mcondition_6'],
['main' => 'mk3', 'secondary' => 'sk5', 'mcondition_pk' => 7, 'mcondition' => 'mcondition_7'],
['main' => 'mk3', 'secondary' => 'sk5', 'mcondition_pk' => 8, 'mcondition' => 'mcondition_8'],
];
foreach($results as $row) {
$mk = $row['main'];
$sk = $row['secondary'];
$pk = $row['mcondition_pk'];
$cond = $row['mcondition'];
$temp = ['id' => $pk, 'text' => $cond];
if(!isset($out[$mk])) { $out[$mk] = ['text' => $mk]; }
if(!isset($out[$mk][$sk])) { $out[$mk][$sk] = ['text' => $sk, 'children' => []]; }
$out[$mk][$sk]['children'][] = $temp;
}
echo "<pre>"; print_r($out); echo "</pre>";
$json = json_encode($out);
echo "<pre>"; print_r($json); echo "</pre>"; exit;