无法在php中安装mysqlnd_uh_set_connection_proxy（）

Question

I try to install mysqlnd_uh_set_connection_proxy() to monitor sql query. However, It doesn't work. It shows a warning.

Warning: mysqlnd_uh_set_connection_proxy(): (Mysqlnd User Handler) You must be using mysqli with mysqlnd. This extension is a mysqlnd plugin. in /var/www/html/test.php on line 15

What should I do? Here is the source code I used:

<?php
class conn_proxy extends MysqlndUhConnection {
 public function query($res, $query) {
  debug_print_backtrace();
  return parent::query($res, $query);
 }
}
class stmt_proxy extends MysqlndUhPreparedStatement {
 public function prepare($res, $query) {
  debug_print_backtrace();
  return parent::prepare($res, $query);
 }
}
mysqlnd_uh_set_connection_proxy(new conn_proxy());
mysqlnd_uh_set_statement_proxy(new stmt_proxy());

printf("Proxies installed...
");

$mysqli = new mysqli("localhost", "root", "root", "shoppingcart");
$mysqli->prepare("SELECT 1 AS _two FROM DUAL");
?>