What is wrong with this code?

<?php
class users {
    

  var $user_id,
  $f_name,
  $l_name,
  $db_host,
  $db_user,
  $db_name,
  $db_table;
  

  function user_input() {
  $this->$db_host = 'localhost';
  $this->$db_user = 'root';
  $this->$db_name = 'input_oop';
  $this->$db_table = 'users';
  }
  

  function userInput($f_name, $l_name) {
  $dbc = mysql_connect($this->db_host , $this->db_user, "") or die ("Cannot connect to database : " .mysql_error());
  mysql_select_db($this->db_name) or die (mysql_error());
  $query = "insert into $this->db_table values (NULL, \"$f_name\", \"$l_name\")";
  $result = mysql_query($query);
  if(!$result) die (mysql_error());

  $this->userID = mysql_insert_id();
  

  mysql_close($dbc);
  

  $this->first_name = $f_name;
  $this->last_name = $l_name;
  }
  

  function userUpdate($new_f_name, $new_l_name) {
  $dbc = mysql_connect($this->db_host, $this->db_user, "") or die (mysql_error());
  mysql_select_db($this->db_name) or die (mysql_error());
  

  $query = "UPDATE $this->db_table set  = \"$new_f_name\" , \"$new_l_name\" WHERE user_id = \"$this->user_id\"";
  $result = mysql_query($query);
  

  $this->f_name = $new_f_name;
  $this->l_name = $new_l_name;
  $this->user_id = $user_id;
  

  mysql_close($dbc);
  }
  

  function userDelete() {
  $dbc = mysql_connect($this->db_host, $this->db_user, "") or die (mysql_error());
  mysql_select_db($this->db_name) or die (mysql_error());
  

  $query = "DELETE FROM $this->db_table WHERE $user_id = \"$this->user_id\"";
  

  mysql_close($dbc);
  } 
  }
?>

The error is:
Warning: mysql_connect() [function.mysql-connect]: Access denied for user 'ODBC'@'localhost' (using password: NO) in C:\xampp\htdocs\jordan_pagaduan\class.php on line 21 Cannot connect to database : Access denied for user 'ODBC'@'localhost' (using password: NO)

The code cannot define this "$this->db_host" as "localhost".