Notice: Undefined variable: mysqli in /home/brzanek/public_html/wykresy2022/1.php on line 15

Fatal error: Uncaught Error: Call to a member function query() on null in /home/brzanek/public_html/wykresy2022/1.php:15
Stack trace:
#0 {main}
  thrown in /home/brzanek/public_html/wykresy2022/1.php on line 15