Trouble with the db connection

I'm trying to retrieve stuff from db, but I'm getting this error:

Code:

Call to undefined function CodeIgniter\Database\MySQLi\mysqli_init()

Code:

SYSTEMPATH/Database\MySQLi\Connection.php at line 107

Code:

107         $this->mysqli = mysqli_init();

My db config:

PHP Code:

public $default = [
        'DSN'      => '',
        'hostname' => '0.0.0.0',
        'username' => 'username',
        'password' => 'p4ssw0rd',
        'database' => 'db_name',
        'DBDriver' => 'MySQLi',
        'DBPrefix' => '',
        'pConnect' => false,
        'DBDebug'  => (ENVIRONMENT !== 'production'),
        'cacheOn'  => false,
        'cacheDir' => '',
                'charset'  => 'utf8mb4',
        'DBCollat' => 'utf8_general_ci',
        'swapPre'  => '',
        'encrypt'  => false,
        'compress' => false,
        'strictOn' => false,
        'failover' => [],
        'port'     => 3306,
    ]; 


The query I'm running:

PHP Code:

$query = $db->query('SELECT * FROM table_name'); 


I have PHP 7.2.4, MySQL 8 in 5 compatibility mode, Windows 10, CI4 beta 1