"Pdo\Mysql object is uninitialized" when opening a persistent connection

[derrabus]

Description

The following code:

<?php

declare(strict_types=1);

$pdo = PDO::connect('mysql:host=127.0.0.1;dbname=test', 'root', '', [PDO::ATTR_PERSISTENT => true]);
$pdo->query('SELECT 1;');

Resulted in this output:

Fatal error: Uncaught Error: Pdo\Mysql object is uninitialized in /path/to/test.php on line 6

Error: Pdo\Mysql object is uninitialized in /path/to/test.php on line 6

Call Stack:
    0.0001     395016   1. {main}() /path/to/test.php:0
    0.0020     395152   2. PDO->query($query = 'SELECT 1;', $fetchMode = ???) /path/to/test.php:7

[1]    65142 bus error  php test.php

But I expected this output instead: No error.

The error is gone if I either set PDO::ATTR_PERSISTENT to false or call the oldschool constructor (new PDO(…)).

PHP Version

PHP 8.4-dev

Operating System

MacOS 15.0.1

[derrabus]

This problem is not limited to MySQL. I can also reproduce it with a Postgres database:

$pdo = PDO::connect('pgsql:host=127.0.0.1;dbname=test', 'postgres', 'postgres', [PDO::ATTR_PERSISTENT => true]);
$pdo->query('SELECT 1;');

Output:

Fatal error: Uncaught Error: Pdo\Pgsql object is uninitialized

Again, if I set PDO::ATTR_PERSISTENT to false or connect via the old constructor, the problem is gone.

[derrabus]

cc @Danack and @kocsismate since the new PDO classes are essentially your baby. Thank you very much for your work on that, by the way. ❤️

[kocsismate]

@derrabus Thank you for the report (and the compliment as well)! I'll start to look into the problem tonight.

[kocsismate]

@derrabus Finally, I merged my changes so that it makes RC4. Thanks for your patience!

[derrabus]

I'm reverting our workaround in doctrine/dbal#6623. Thank you very much for fixing the bug. 🙏🏻