note 123650 added to book.mysqli

I can no longer use this: $myusername = mysqli_string($db,$_POST['username']); $mypassword = mysqli_string($db,$_POST['password']); I'm using PHP 5.6.36. I'm getting these errors: Undefined index: username and Undefined index: password. What should I do? I can't integrate my login page to my home page. ---- Server IP: 208.43.231.9 Probable Submitter: 185.85.3.142 (proxied: 119.92.118.131) ---- Manual Page -- http://php.net/manual/en/book.mysqli.php Edit -- https://master.php.net/note/edit/123650 Del: integrated -- https://master.php.net/note/delete/123650/integrated Del: useless -- https://master.php.net/note/delete/123650/useless Del: bad code -- https://master.php.net/note/delete/123650/bad+code Del: spam -- https://master.php.net/note/delete/123650/spam Del: non-english -- https://master.php.net/note/delete/123650/non-english Del: in docs -- https://master.php.net/note/delete/123650/in+docs Del: other reasons-- https://master.php.net/note/delete/123650 Reject -- https://master.php.net/note/reject/123650 Search -- https://master.php.net/manage/user-notes.php