Warning: mysqli_connect(): (HY000/2002): Connection refused in /www/wwwroot/liuxue/www2/common.php on line 21

Fatal error: Uncaught TypeError: mysqli_select_db(): Argument #1 ($mysql) must be of type mysqli, bool given in /www/wwwroot/liuxue/www2/common.php:22 Stack trace: #0 /www/wwwroot/liuxue/www2/common.php(22): mysqli_select_db() #1 /www/wwwroot/liuxue/www2/common.php(26): connectmysqli() #2 /www/wwwroot/liuxue/www2/sitemap.php(5): require('...') #3 {main} thrown in /www/wwwroot/liuxue/www2/common.php on line 22