로그인 시 오류가 납니다

로그인 또는 회원가입을 누르면 하얀 창에 이런 글이 쓰인 페이지로 이동합니다.

도움 주세요ㅠㅠ

Warning: include_once(./_common.php): failed to open stream: No such file or directory in E:\APM_Setup\htdocs\bbs\login_check.php on line 2 Warning: include_once(): Failed opening './_common.php' for inclusion (include_path='.') in E:\APM_Setup\htdocs\bbs\login_check.php on line 2 Notice: Use of undefined constant mb_id - assumed 'mb_id' in E:\APM_Setup\htdocs\bbs\login_check.php on line 4 Notice: Use of undefined constant mb_password - assumed 'mb_password' in E:\APM_Setup\htdocs\bbs\login_check.php on line 5 Fatal error: Call to undefined function get_member() in E:\APM_Setup\htdocs\bbs\login_check.php on line 20