Get multilevel json from mysql db and php - php

Question

I have the tables
I want to retrieve a json string of the format
[{
"topic_id":"1",
"topic_title":"Input and Output devices",
"topic_image":"inputs.png",
"subtopics": {
"subtopic_id":"1",
"subtopic_title":"Inputs",
"subtopic_file_url":"0"
},
{
"subtopic_id":"2",
"subtopic_title":"Outputs",
"subtopic_file_url":"0"
}
}]
What I tried
// set the resulting array to associative
$result = $stmt->fetchAll(\PDO::FETCH_ASSOC);
foreach ($result as $key => $value) {
$topic[$key]['topic_id'] = $value['topic_id'];
$topic[$key]['topic_title'] = $value['topic_title'];
$topic[$key]['topic_image'] = $value['topic_image'];
$topic[$key]['subtopics']['subtopic_id'] = $value['subtopicid'];
$topic[$key]['subtopics']['subtopic_title'] = $value['subtopic_title'];
$topic[$key]['subtopics']['subtopic_file_url'] = $value['file_url'];
$topic[$key]['subtopics']['subtopicid'] = $value['subtopicid'];
}
print 'PHP_ARRAY: ';print_r($topic);
$topic = json_encode ( $topic );
The script above returns topic details for each subtopic.

Answer 1

This code has worked. Thank you everyone
<?php
$servername = "***";
$username = "****";
$password = "***";
$dbname = "****";
function searchForId($id, $array) {
foreach ($array as $key => $val) {
if ($val['topic_id'] === $id) {
return $key;
}
}
return null;
}
try {
$conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$stmt = $conn->prepare("select a.topic_id, a.topic_title, a.topic_image, b.subtopicid,b.subtopic_title,b.file_url from topics a join subtopics b on b.topic_id = a.topic_id ");
$stmt->execute();
// set the resulting array to associative
$result = $stmt->fetchAll(\PDO::FETCH_ASSOC);
$x = 0;
foreach ($result as $key => $value) {
if($x != 0){
if($topic[$x-1]['topic_id'] != $value['topic_id']) {
$topic[$x]['topic_id'] = $topic_id = $value['topic_id'];
$topic[$x]['topic_title'] = $value['topic_title'];
$topic[$x]['topic_image'] = $value['topic_image'];
$x++;
}
} else {
$topic[$key]['topic_id'] = $topic_id = $value['topic_id'];
$topic[$key]['topic_title'] = $value['topic_title'];
$topic[$key]['topic_image'] = $value['topic_image'];
$x++;
}
}
$x = $y = 0;
foreach ($result as $key => $value) {
if($y != searchForId($value['topic_id'], $topic))
$x = 0;
$y = searchForId($value['topic_id'], $topic);
$topic[$y]['subtopics'][$x]['subtopic_id'] = $value['subtopicid'];
$topic[$y]['subtopics'][$x]['subtopic_title'] = $value['subtopic_title'];
$topic[$y]['subtopics'][$x]['subtopic_file_url'] = $value['file_url'];
// $topic[$y]['subtopics'][$x]['subtopicid'] = $value['subtopicid'];
$x++;
}
// foreach ($result as $key => $value) {
// }
//print 'PHP_ARRAY: ';print_r($topic);
$topic = json_encode ( $topic );
print_r($topic);
}
catch(PDOException $e) {
echo "Error: " . $e->getMessage();
}
$conn = null;
?>