当开启事务的情况
获取lastid语句写在commit之后lastid返回的是0
$dbh->beginTransaction();
$stmt->execute( array($data ['openid'], $createTime));
$dbh->commit();
$lastid = $dbh->lastInsertId();
获取lastid语句写在commit之前lastid返回的是自增id
$dbh->beginTransaction();
$stmt->execute( array($data ['openid'], $createTime));
$lastid = $dbh->lastInsertId();
$dbh->commit();