Query still running even after page timeout

I needed to update all of my users with some settings in a new table.

I wrote this:

$users = User::all();

        foreach($users as $u) {
            $settings = Settings::query()->where('user_id', $u->id)->doesntExist();

            if ($settings) {

                $s = new Settings();
                $s->user_id = $u->id;
                $s->show_alltime_stats = 1;
                $s->show_time_listened = 1;
                $s->save();

            }
        }

What I'm trying to do is

• Get all users from users table.
• Check if they exist in the settings table.
• If they don't exist, add them.

Now This was quick and dirty and I didn't use a queue or jobs or anything. just ran this as you see it.

Strange thing after several seconds the page times out, but I noticed the query keeps going. Whats even worse is it took me a few goes to realise this, so users are being created in the settings table multiple times.

Could someone explain to me what madness is going on here? I mean even IF the script were to keep running, I would have thought my code would prevent users being added multiple times.

Any and all help appreciated. I'd like to understand what I've done.