PDO FETCH_CLASS with joined tables - php

Question

Let's say I have 2 php objects:
<?php
class Post {
public $id;
public $text;
public $user_id;
}
?>
and
<?php
class User {
public $id
public $name
}
?>
Every post has a unique constraint with 1 user in the database.
I want to fill data into the "Post"-object with PDOs "FETCH_CLASS" method which works for all the "Post" attributes but how do I fill the attributes in "User"?
My SQL-statement looks like this:
SELECT post.id,
post.text,
post.user_id,
user.id,
user.name
FROM POST INNER JOIN User on post.user_id = user.id
Thanks!
UPDATE:
ATM I fill my "Post"-class like this:
$statement = $db -> prepare($query);
$statement -> execute();
$statement -> setFetchMode(PDO::FETCH_CLASS, 'Post');
$posts = $statement -> fetchAll();
So how would I have to change that for also filling the other class "User"?
SOLUTION:
$statement = $db -> prepare($query);
$statement -> execute();
$posts = array();
while (($row = $statement->fetch(PDO::FETCH_ASSOC)) !== false) {
$post = new Post();
$post->id = $row['post_id'];
$post->text = $row['post_text'];
$post->created = $row['post_created'];
$post->image = $row['post_image'];
$post->url = $row['post_url'];
$post->weight = $row['post_weight'];
$post->likes = $row['post_likes'];
$user = new User();
$user->id = $row['user_id'];
$user->nickname = $row['user_nickname'];
$user->created= $row['user_created'];
$user->locked = $row['user_locked'];
$post->user = $user;
$posts[] = $post;
}
return $posts;

Answer 1

You can try using __set method like this:
<?php
include 'connection.php';
class Post {
public $id;
public $text;
public $user;
public function __construct() {
$this->user = new User();
}
public function __set($name, $value) {
if (array_key_exists($name, get_object_vars($this->user))) {
$this->user->$name = $value;
} else {
$this->$name = $value;
}
}
}
class User {
public $id;
public $name;
}
$statement = $pdo->prepare("SELECT * FROM post "
. "LEFT JOIN user "
. "ON post.user_id = post.id");
$statement->execute();
$result = $statement->fetchAll(\PDO::FETCH_CLASS | \PDO::FETCH_PROPS_LATE, Post::class);
echo "<pre>";
var_dump($result);

Answer 2

Theres no support for the directly in PDO as far as I'm aware. Typically if you need to create a complex object graph from the result of query thats the responsibility of an ORM.
If you need this functionality i wold recommend using Doctrine or Propel as opposed to writing something yourself. There are others too that may be lighter weight, but i have no experience with them.
EDIT:
I think maybe i misunderstood the question as im sure others might. I think the real question was how to get access to the joined columns, not cessarially how to create an object from them.
In that case simply using a standard arry fethc method like PDO::FETCH_ASSOC, PDO::FETCH_NUMERIC or PDO::FETCH_BOTH will give you all the columns you queried.
So if you want to turn that into an "object graph" you have to do it manually not by using PDO::FETCH_CLASS.
For example:
//$db is pdo:
// also notice im aliase the columns prefixing the name so that we can tell what belongs to
// post and what belongs to user, an alternative approach would be to use FETCH_NUMERIC,
// which just uses the column positions from the seelct statement as the keys
// so in this case post.id would be in the array as key 0, and user.name would be in the
// array as key 4
$stmt = $db->prepare('SELECT post.id as p_id,
post.text as p_text,
post.user_id as p_user_id,
user.id as u_id,
user.name as u_name
FROM POST INNER JOIN User on post.user_id = user.id');
$stmt->execute();
while (($row = $stmt->fetch(PDO::FETCH_ASSOC)) !== false) {
print_r($row);
/* will output:
Array (
'p_id' => 'value'
'p_text' => 'value'
'p_user_id' => 'value'
'u_id' => 'value',
'u_name' => 'value'
)
So now you need to decide how to create your objects with the information returned
*/
}

Answer 3

Not really a response for the OQ, but because it keeps popping on Google (yes I know its over a year old). You'll find that it is AMAZINGLY faster to just skip loops and query each table separately.
SELECT post.id,
post.text,
post.user_id,
FROM POST INNER JOIN User on post.user_id = user.id
$statement = $db -> prepare($query);
$statement -> execute();
$statement -> setFetchMode(PDO::FETCH_CLASS, 'Post');
$posts = $statement -> fetchAll();
SELECT user.id,
user.name
FROM POST INNER JOIN User on post.user_id = user.id
$statement = $db -> prepare($query);
$statement -> execute();
$statement -> setFetchMode(PDO::FETCH_CLASS, 'User');
$users = $statement -> fetchAll();

Answer 4

Maybe use PDO::FETCH_NAMED if you work multiple tables. Or use PDO::ATTR_FETCH_TABLE_NAMES.

Answer 5

My approach for solution:
function groupQueryJoinClasses(\PDOStatement $stmt, $joinInfo = [], $idProperty = 'id')
{
$result = [];
$records = $stmt->fetchAll();
if ( !empty($joinInfo) ) {
foreach ($records as $record) {
if ( !isset($result[$record->$idProperty]) ) {
$result[$record->$idProperty] = $record;
}
foreach ($joinInfo as $target => $classInfo) {
$vars = get_object_vars($record);
$class = new $classInfo['class']();
foreach ($vars as $key => $value) {
$keyData = explode('.', $key);
if ( $keyData[0] == $classInfo['prefix']) {
$class->$keyData[1] = $value;
unset($result[$record->$idProperty]->$key);
}
}
if ( !is_array( $result[$record->$idProperty]->$target) ) {
$result[$record->$idProperty]->$target = [];
}
$targetArray = &$result[$record->$idProperty]->$target;
$targetArray[] = $class;
}
}
} else {
$result = $records;
}
return $result;
}
function getModel($query, $data, $entryClass, $joinInfo, $idProperty = 'id') {
$pdo = new PDO(...);
$stmt = $pdo->prepare($query);
$stmt->execute($data);
$stmt->setFetchMode(\PDO::FETCH_CLASS, $entryClass);
return groupQueryJoinClasses($stmt, $joinInfo , $idProperty);
}
// Sample request
$query =
'SELECT
u.id as "id",
p.id as "Post.id",
p.name as "Post.name"
FROM `user` u
LEFT JOIN `posts` p ON p.user_id = u.id
where id = :id'
;
$data = [ ':id' => 1 ];
$joinInfo = [
'posts' => [
'class' => Post::class,
'prefix'=> 'Post'
]
];
$flowRules = getModel($query, $data, User::class, $joinInfo);
Maybe interesting for anyone, or maybe someone would see issue in such approach