How to access mysql container from php container?

Question

Docker

I want to make a script that makes backups of the database and saves it in a certain path by running cron 2 times a day.
Using Laravel, I put a command in vps in the cron file that will pull other cron commands that I will create through Laravel:

* * * * * docker exec app /var/www/artisan schedule:run >> /dev/null 2>&1

And the question is - if in fact this command is run through the php container, and I want to execute the mysqldump command, which should be run directly from the mysql container, how to organize this?
The method that makes the backup looks like this:

$filename = 'backup-' . date("Y-m-d_h_i_s") . '.sql';
        $command = "docker exec db mysqldump --user=" . env('DB_USERNAME') ." --password=" . env('DB_PASSWORD') . " " . env('DB_DATABASE') . "  | gzip > " .  "/var/backups/" . $filename;
        $returnVar = null;
        $output  = null;
        exec($command, $output, $returnVar);

But, saving does not occur :(
However, if I execute this command in the VPS itself, then everything is saved. As I understand it, I need to somehow knock from one container to another container, how to do this?

Answer 1

Maybe it's easier to separate?

* * * * * docker exec db mysqldump ... && docker exec app ...

Answer 2

Do I understand correctly that the IP addresses (or domain names) of the containers are different? Add the host parameter so you can link the two containers and you'll be good to go.