PHP returns false when calling redis method decrby less than 0

    public function decr($key, $val = 1, $lessZero = false)
    {
        if ($lessZero) {
            $luaScript = <<<LUA
if tonumber(redis.call("get", KEYS[1])) > 0 then
    return redis.call('decrBy', KEYS[1], ARGV[1])
else
    return false
end
LUA;
            //
            $res = $this->redis->eval($luaScript, [$key, $val], 1);
        } else {
            //
            $res = $this->redis->decrBy($key, $val);
        }
        //
        return $res;
    }