Some of the problems left over from last night have been solved. Please give me some advice on the rest.

Question

数据库连接成功！ Notice:  Use of undefined constant vote_name - assumed 'vote_name' in C:\phpStudy\PHPTutorial\WWW\test\Voteset.php on line 4

Notice:  Undefined variable: db in C:\phpStudy\PHPTutorial\WWW\test\Voteset.php on line 18

Fatal error:  Call to a member function query() on a non-object in C:\phpStudy\PHPTutorial\WWW\test\Voteset.php on line 18