PDO - get from one to many structure - php

Question

I have this db structure:
create table article(
id int AUTO_INCREMENT PRIMARY KEY,
title varchar(50),
text text
)
create table comments(
id int AUTO_INCREMENT PRIMARY KEY,
article int not null
username varchar(30) not null,
text text not null,
foreign key(article) references article(id) on delete cascade
)
I would like to get articles with comments and convert to json with this structure:
[
{
id: 1,
title: "article1",
text: "text1",
"comments": [
{
id: 1,
username: "user1",
text: "text"
}
]
}
]
This is my code:
$query = $pdo->query('select * from article as a join comments as c on c.article =a.id');
$query->execute();
var_dump(json_encode($query->fetchAll(PDO::FETCH_ASSOC)));
and result:
[{"id":"1","title":"artile1","text":"comment1","article":"1","username":"user1"}]
It is any way how to get article and comments as inner array? I could do it manually but, I will have a lot of tables with many columns.
Thanks for advices

Answer 1

It looks like it is not possible using PDO fetch modes. They are powerful, but unfortunately, I was not able to get the output you wanted.
You can achieve this outcome using a simple loop. The downside is that you have to create the array manually.
$stmt = $pdo->prepare('SELECT a.id AS aid, a.title, a.text AS atext, c.id AS cid, c.username, c.text AS ctext
FROM article AS a
JOIN comments AS c ON c.article =a.id ');
$stmt->execute();
$stmt->setFetchMode(PDO::FETCH_ASSOC);
$id = null;
$data = [];
foreach ($stmt as $row) {
$comment = [
'id' => $row['cid'],
'username' => $row['username'],
'text' => $row['ctext'],
];
if ($id == $row['aid']) {
// If parent ID still the same append only comment
$data[array_key_last($data)]['comments'][] = $comment;
} else {
// set new id and append a whole new row
$id = $row['aid'];
$data[] = [
'id' => $row['aid'],
'title' => $row['title'],
'text' => $row['atext'],
'comments' => [$comment]
];
}
}
PDO has plenty of fetch modes and you can mix them together, but it looks like none of them can cope with joins the way you would like them too. They are all described here in https://phpdelusions.net/pdo/fetch_modes