سا اعطيك نموذج اخر وهو الدخول للوحة التحكم ومنع اي شخص من دخولها حتى يكون ادمين

<?php

session_start();

class mysql{

private $localhost="localhost";
private $db_user="root";
private $db_pass="root";
private $db_name="users";


function __construct(){
    mysql_connect($this->localhost,$this->db_user,$this->db_pass);
    mysql_select_db($this->db_name);              
}

function sql(){

    $username=$_POST['username'];
    $password=$_POST['password'];

    $sql="SELECT * FROM user WHERE username='$username' AND password='$password'";
    $query=mysql_query($sql);
    $num=mysql_num_rows($query);

   if ($num>0){
        $_SESSION['username']="username";
        $_SESSION['password']="password";   
        echo"       
        <meta http-equiv='refresh' content='2; url=admin.php' />
        ";
    }else{

        echo "bad";
        echo "
   <meta http-equiv='refresh' content='2; url=login.php' />

";

}

}    

}

$use=new mysql; $use->sql();

?>

اما هنا لوحة النحكم

<?

if (isset($_SESSION['username'])){ echo "welcome admin";

}else{ echo "login please";

}

?>