add_menu_page does not seem to work in a class

From add_menu_page in Codex:

Note: If you’re running into the “You do not have sufficient permissions to access this page” error, then you’ve hooked too early. The hook you should use is admin_menu.

admin_init is too early to hook add_menu_page, use admin_menu.

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)