Object oriented programming in php

<?php
/**********************************************************************
     * Author    :  Anil Kumar Panigrahi
     * E-mail    :   [email protected]
     * Created on:  6th June 2011
     * Version   :  1.0
     * Project   :   Database Interactions
     * Page      :  User Class
     * Company   :   Anil Labs  (https://www.anillabs.com)
     * Modified on :  
     * Modified by :  
*************************************************************************/

class Users{
     
    /*****************************************************************
      Users is a constructor to establish the database connection
     *****************************************************************/
    private $dbHost;
    private $dbUser;
    private $dbPassword;
    private $dbName;
    private $first_name;
    private $last_name;
    private $user_name;
    private $password;
    private $id;
    private $con;
    public function __construct($dbHost,$dbUser,$dbPassword,$dbName){
        $this->dbHost = "{DATABASE SEVER}";
        $this->dbUser = "{USERNAME}";
        $this->dbPassword="{PASSWORD}";
        $this->dbName= "{DBNAME}";
        $mysqli = new mysqli($this->dbHost,$this->dbUser,$this->dbPassword,$this->dbName);
        /* check connection */
        if (mysqli_connect_errno()) {
            printf("Connect failed: %s\n", mysqli_connect_error());
            exit();
        }
    }
   
    /*****************************************************************
      insert function to insert data into database
     *****************************************************************/
   
    public function insert ($first_name,$last_name,$user_name,$password){
               
        $stmt1 = $mysqli->prepare("INSERT INTO USERS VALUES (?, ?,?,?)");
        $stmt1->bind_param('ssss', $this->first_name,$this->last_name,$this->user_name,$this->password);
        $this->first_name=$first_name;
        $this->last_name=$last_name;
        $this->user_name=$user_name;
        $this->password=$password;
        $stmt1->execute();
        $stmt1->close();       
        $id = $mysqli->insert_id;
        return $id                     
    }
   
    /*****************************************************************
      udpate function to update data into database
     *****************************************************************/
   
    public function update($id,$first_name,$last_name,$user_name,$password){
       
        $stmt1 = $mysqli->prepare("UPDATE INTO USERS first_name=?,last_name=?,user_name=?,password=? where user_id=?");
        $stmt1->bind_param('ssssi', $this->first_name,$this->last_name,$this->user_name,$this->password,$this->id);
        $this->first_name = $first_name;
        $this->last_name= $last_name;
        $this->user_name= $user_name;
        $this->password= $password;
        $this->id= $id;
        $result=$stmt1->execute();
        $stmt1->close();
        if($result) return true;
        else return false;
                                       
    }
   
    /*****************************************************************
      delete function to dalete data from database
     *****************************************************************/
    public function delete($id){
       $stmt1 = $mysqli->prepare("DELETE FROM USERS WHERE user_id =?");
       $stmt1->bind_param('i', $this->id);
       $this->id= $id;
       $result=$stmt1->execute();
       $stmt1->close();
       if($result) return true;
        else return false;
    }
   
    /*****************************************************************
      retrieve function to get data from database
     *****************************************************************/
     
    public function retrieve($id){
       $stmt1 = $mysqli->prepare("SELECT * FROM USERS WHERE user_id =?");
       $stmt1->bind_param('i', $this->id);
       $this->id= $id;
       $result=$stmt1->execute();
       $stmt->bind_result($first_name, $last_name,$user_name,$password);
       while ($stmt->fetch()) {
        printf ("%s ,%s,%s,%s\n", $first_name, $last_name,$user_name,$password);
       }
       $stmt1->close();
    }
    public __destruct() {
             unset($this->dbHost);
             unset($this->dbUser);
             unset($this->dbPassword);
             unset($this->dbName);
             unset($this->first_name);
             unset($this->last_name);
             unset($this->user_name);
             unset($this->password);
             unset($this->id);
             $mysqli->close();
             unset($this->con);
       }
   
}


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