无法连接.太多的联系”;mysql错误

我有以下代码

function openDBConn($params){
    $conn_mode = $params['conn_mode'];
    $db_conn = $params['db_conn'];
    //create connections
    if(empty($db_conn->info)) {
        $db_conn = new mysqli("localhost", $user, $password, "database");
        $db_conn->set_charset('UTF8'); 
        $mysqli_error = $db_conn->connect_error;
    }
    if($mysqli_error !== NULL){ 
        die('Could not connect <br/>'. $mysqli_error); 
    }else{ 
        return $db_conn; 
    }
}
//close db connection
function closeDBConn( $params ){
    $db_conn = $params['db_conn'];
    $db_conn->close;
}
//used as below
$db_conn = openDBConn();
save_new_post( $post_txt, $db_conn );
closeDBConn( array('db_conn'=>$db_conn));

不时地，我得到"无法连接"。连接太多"错误。当我让谷歌机器人扫描我的网站时，这种情况往往会发生。

这个问题似乎从MySQL升级到MySQLi就开始了。有什么建议，如何确保所有连接关闭?

谢谢