How do I put extra number at the end of username if duplicate

Question

Hard to explain, and let me show an example.

1. If username foo already exists in MySQL I want php script will allow it but to be foo1

Answer 1

    while (exists($username)) {
        if (!is_numeric(substr($username, -1, 1))) {
            $username = "{$username}0";
        }
        $username++;
    }

    return $username;

You get: test, test1, test2 and so on