Description:
------------
My php version is 8.0.0 ,mysql version is 8.0.22, apache version is 2.4.46

Output is as follows  
object(mysqli)#8 (18) {
  ["affected_rows"]=>
  int(0)
  ["client_info"]=>
  string(13) "mysqlnd 8.0.0"
  ["client_version"]=>
  int(80000)
  ["connect_errno"]=>
  int(0)
  ["connect_error"]=>
  NULL
  ["errno"]=>
  int(0)
  ["error"]=>
  string(0) ""
  ["error_list"]=>
  array(0) {
  }
etc
.......

after type casting everything returns null 

array(18) {
  ["affected_rows"]=>
  NULL
  ["client_info"]=>
  NULL
  ["client_version"]=>
  NULL
  ["connect_errno"]=>
  NULL
  ["connect_error"]=>
  NULL
  ["errno"]=>
  NULL
  ["error"]=>
  NULL
  ["error_list"]=>
  NULL
etc
....

Test script:
---------------
//Type casting of mysqli object to array produces null on every field on var_dump() and print_r()

$db = mysqli_connect(hostname:'localhost',username:'root',password:'',database:'tables',port:3306);

echo "<pre>";    // We get output in this case even with var_dump
print_r($db);
echo "</pre>";

echo "<pre>";
print_r((array) $db);  // All fields show null even with var_dump
echo "</pre>";