Warning: mysqli_query() expects parameter 1 to be mysqli, null given in /home/htdocs/school/functions/general_mysql.php on line 30

Fatal error: Uncaught Error: Call to undefined function mysql_num_rows() in /home/htdocs/school/school.php:114
Stack trace:
#0 {main}
  thrown in /home/htdocs/school/school.php on line 114