The constructor (__construct) is called automatically when an object is created. The destructor (__destruct) is called when the object is destroyed (goes out of scope, or when the script ends).
<?php
class DatabaseConnection
{
private \PDO $pdo;
private static int $instanceCount = 0;
public function __construct(
private string $dsn,
private string $user,
private string $pass
) {
// Constructor body runs after property promotion
$this->pdo = new \PDO($this->dsn, $this->user, $this->pass, [
\PDO::ATTR_ERRMODE => \PDO::ERRMODE_EXCEPTION,
\PDO::ATTR_DEFAULT_FETCH_MODE => \PDO::FETCH_ASSOC,
]);
self::$instanceCount++;
echo "Connection opened. Total: " . self::$instanceCount . "
";
}
public function query(string $sql, array $params = []): array
{
$stmt = $this->pdo->prepare($sql);
$stmt->execute($params);
return $stmt->fetchAll();
}
public function __destruct()
{
// Called when object goes out of scope or script ends
self::$instanceCount--;
echo "Connection closed. Remaining: " . self::$instanceCount . "
";
// \PDO closes the connection when $this->pdo is garbage-collected
}
}
$db = new DatabaseConnection('mysql:host=localhost;dbname=shop', 'root', 'secret');
// ... use $db ...
// When $db goes out of scope, __destruct is called automatically
unset($db); // forces immediate destruction
Tip: Destructors are not guaranteed to run at a specific time — the PHP garbage collector decides when to collect objects. Do not rely on __destruct for critical clean-up logic; use explicit close() / disconnect() methods called in finally blocks instead.