Use a closure for the PDO FETCH instructions - php

Question

It occurs to me that I want to give my PDO result the instructions on how to instantiate itself into an object when it gets iterated later on, but I do not want to perform the logic until that time.
I've been looking for the existence of this PDO functionality but I cannot find it. What I want to do is essentially this:
public function getUsers()
{
$sql = 'select first_name, last_name, phone, address from users';
return $this->pdo->query($sql, PDO::FETCH_ASSOC, function($row) {
$user = new User();
$user->setName($row['first_name'] . ' ' .$row['last_name'])
->setPhoneNumber($row['phone'])
->setMailingAddress($row['address']);
return $user;
});
}
Is there a good way of accomplishing this with PHP and specifically PDO? Looping through the iterator is not an acceptable answer. I only want to iterate on this recordset once during execution.

Answer 1

You can use a Generator for this via yield. Only when the internal pointer is on certain iteration, the concrete object will be yielded.
class User {
public $picture;
public function __construct($pic) {
$this->picture = $pic;
}
}
function getUsers() {
$pdo = new PDO('mysql:host=localhost;dbname=users', 'root', '');
$query = "SELECT * FROM votesusers";
$res = $pdo->query($query);
while ($row = $res->fetch()) {
yield new User($row['picture_id']);
}
}
foreach (getUsers() as $user) {
var_Dump($user);
}
Output:
object(User)[5]
public 'picture' => string '2' (length=1)
object(User)[6]
public 'picture' => string '9' (length=1)
object(User)[5]
public 'picture' => string '6' (length=1)
object(User)[6]
public 'picture' => string '1' (length=1)

Answer 2

You can create a custom lazy-loading collection that implements the Iterator interface. Here's an example:
class LazyCollection implements Iterator
{
private $stmt;
private $callback;
public function __construct(PDOStatement $stmt, Closure $callback)
{
$this->stmt = $stmt;
$this->callback = $callback;
}
public function current()
{
$callback = $this->callback; // required because PHP is silly
return $callback($this->stmt->fetch());
}
/* rest of interface implementation */
}
And you would use it like this:
$stmt = $this->pdo->query($sql, PDO::FETCH_ASSOC)
$result = new LazyCollection($stmt, function($row) {
return new User($row['name'], $row['phone'], $row['address']);
});
foreach($result as $user)
{
// $user is an instance of User
}

Answer 3

Probably something like this:
$result = $this->pdo->query($sql, PDO::FETCH_CLASS, 'User');
return $result->fetch();