Re: [PHP-DEV] `COM_RESET_CONNECTION` support in `mysqlnd`

On Tue, May 19, 2026 at 6:55 AM <[email protected]> wrote:
>
> > Personally, given that both of these versions are EOL, this feels
> > acceptable, but I'm curious what others think. Notably, if we were to
> > implement configuration for this we'd likely need to introduce yet
> > another INI variable; I have an impression that PHP maintainers are
> > somewhat skeptical of adding new INI settings.
>
> I think it's ok to drop support of EOL versions. But I also think it's possible to support both new and ancient mysql even without any runtime options (ini setting, PDO constant et al). First try to send `COM_RESET_CONNECTION` and if server return error, try `COM_CHANGE_USER`. Result of this check may be cached for improved performance, but not strictly necessary. This at least won't break anyone.
>
> But if you are feel strongly about completely dropping `COM_CHANGE_USER`, then some deprecation period should exist. Users should see at least `E_DEPRECATED` errors in their logs before day X. I know about changelog page and NEWS file, but among all the PHP programmers I know, no one reads them.

I don't know that I feel strongly, but I also don't think it's worth
the complexity of a dual check and deprecation notice for (what I
imagine is) the small subset of users who want modern PHP but not
modern database software.

> > Secondly, I'm curious what people think about implementing this in
> > both PDO *and* `mysqlnd`. In PDO, we can replace the liveness check
> > with this command, which would act as both a liveness check and a
> > reset for no additional round-trip cost.
>
> It's ok to replace liveness check with reset, but I think you choose wrong place for implementation. You changed the `pdo_mysql_check_liveness` function and now it not just "liveness check", which leads to a discrepancy with its name and also liveness functions from other PDO drivers. I'd rather implement in on PDO level. Something like:
>
> ```c
> // pdo_dbh.c:420
> /* is the connection still alive ? */
> - if (pdbh->methods->check_liveness && FAILURE == (pdbh->methods->check_liveness)(pdbh)) {
> + if (!(pdbh->methods->reset && (pdbh->methods->reset)(pdbh)) && pdbh->methods->check_liveness && FAILURE == (pdbh->methods->check_liveness)(pdbh)) {
>      /* nope... need to kill it */
>      pdbh->refcount--;
>      zend_list_close(le);
>      pdbh = NULL;
>  }
> ```

Great catch, I'm somewhat embarrassed I didn't notice this myself. I
took your suggestion and updated the PR to include a new "reset
connection" hook for PDO that currently only mysqlnd implements. Thank
you!