php（ssh2，tunnel），我无法连接我的远程mysql服务器

<?
   $server_ip = "my ubuntu ip";
   $server_port = "my ubuntu port";
   $server_user = 'my id';
   $user_pw = 'my pw';
   $connection = ssh2_connect($server_ip, $server_port);
   if (ssh2_auth_password($connection, $server_user, $user_pw)) {
     echo "Authentication Successful!<br>";
   } else {
     echo "Authentication failed...";
   }

   $mysql_ip = '10.41.12.71';
   $mysql_default_port = '3306';

   $tunnel = ssh2_tunnel($connection,$mysql_ip,$mysql_default_port);
   if($tunnel) {
       echo "tunnel created<br>";
   }else {
       echo "tunnel creation failed";
       die();
   }

   $mysql_user = 'root';
   $mysql_user_pw = 'tkakcy159*';
   $dbname = 'test';
  //  $dbconn = mysqli_connect($tunnel,$mysql_user,$mysql_user_pw,$dbname);
   $dbconn = new mysqli($tunnel, $mysql_user, $mysql_user_pw, $dbname);
   if ($dbconn) {
    echo $dbname." connected<br>";
  } else {
    echo "DBConnection failed: " . $dbconn->connect_error;
  }

  // $insert_sql = " insert into test_table values('0001','wlsdhks0423'); ";
  // $result = mysqli_query($dbconn,$insert_sql);
  // if($result) {
    //  echo "data insert success<br>";
    // }
    // else {
  //   echo "data insert failed : ".mysqli_error($dbconn);
  // }

  $select_sql = " select * from test_table; ";
  $result = mysqli_query($dbconn,$select_sql);

  if($result) {
    echo "selected rows : ".mysqli_num_rows($result)."<br>";
    $row = mysqli_fetch_array($result);
    $key = $row['test_key'];
    $value = $row['test_value'];
    echo "key = ".$key."<br>value = ".$value;
  }else {
    echo mysqli_error($dbconn);
  }


   // phpinfo();
?>

This is my code. mysql is on ubuntu device. And I think I can access ubuntu, but mysql connection is failed

this php's output is

Authentication Successful!
tunnel created
test connected

and if i use this line

$dbconn = mysqli_connect($tunnel,$mysql_user,$mysql_user_pw,$dbname);

then output is

Authentication Successful!
tunnel created
DBConnection failed:

The obvious thing is that $connection and $tunnel has no problem. I had tested them. And works well.

please help me!

This is an exact duplicate of the postgresql question because they both exist for the same reason. You're both trying to connect a service over a SSH Tunnel by using ssh2_tunnel incorrectly.

ssh2_tunnel returns a resource aka a file pointer