function zPop($key)
    {
        $script = <<<EOD
local v = redis.call('zrange', KEYS[1], 0, 0);
if v[1] ~= nil then
    redis.call('zremrangebyrank', KEYS[1], 0, 0);
    return v[1];
end;
return nil;
EOD;
        return $this->cache->eval($script, [$key], 1);
    }