...
$db = new db;
...
$sql = "select * from `news`;
$db->query($sql);

while($result = $db->fetch_array()) {
        $data[] = $result;
}
...
...
function query($sql) {
    ... sql validation etc...

    ... connection happens in a nother function but for my example i wrote it down here...
    $connection = mysqli_connect($host,$db_user,$db_password);
    mysqli_select_db($database);
    return mysqli_query( $connection , $sql);
}

function fetch_array($resp = 0, $assoc = 1) {
    ...validity checks of resp and assoc...
    return mysqli_fetch_array($rp, $assoc);
}
...