Fatal error: Uncaught TypeError: mysqli_query(): Argument #1 ($mysql) must be of type mysqli, null given in C:\xampp\htdocs\pagina\sliders.php:9 Stack trace: #0 C:\xampp\htdocs\pagina\sliders.php(9): mysqli_query(NULL, 'SELECT * FROM s...') #1 {main} thrown in C:\xampp\htdocs\pagina\sliders.php on line 9