It's always this problem

Question

Warning: mysqli_set_charset() expects parameter 1 to be mysqli, resource given in

Answer 1

Classmate, official manual link: http://php.net/manual/zh/mysqli.set-charset.php

bool mysqli_set_charset ( mysqli $link , string $charset ), requires two parameters. Your problem should be caused by failure to connect to the database, so you can test whether the connection to the database is successful