乱码问题：
$conn->query("Set Names 'gb2312'");
或使用iconv函数.
----------------------------------
连接数据库出现:
Client does not support authentication protocol requested
by server; consider upgrading MySQL client
---------------------------------
解决：
one:
mysql> SET PASSWORD FOR
-> 'some_user'@'some_host' = OLD_PASSWORD('newpwd');
two:
mysql> UPDATE mysql.user SET Password = OLD_PASSWORD('newpwd')
-> WHERE Host = 'some_host' AND User = 'some_user';
mysql> FLUSH PRIVILEGES;