区分管理员和用户的登录系统

我有一个登录系统，我想从用户区分管理员，我有一个字段在我的表，需要一个值0或1来区分。问题是我不知道如何区分登录，以便稍后我可以对按钮进行一些限制。我该如何设置这些限制呢?

<?php
//short_open_tag = true;
error_reporting(E_ALL); 
ini_set('display_errors', 1);
 if($_POST)
{
$host="xxxxx"; // Host name 
$username="xxxx"; // Mysql username 
$password="xxxxx"; // Mysql password 
$db_name="xxxx"; // Database name 
$tbl_name="utilizador";

// Connect to server and select databse.
$link = mysqli_connect("$host", "$username", "$password")or die("cannot connect"); 
mysqli_select_db($link , $db_name)or die("cannot select DB");

    $tbl_name="utilizador"; // Table name 
    $username = mysqli_real_escape_string( $link , $_POST['username']);
    $encrypted_password = mysqli_real_escape_string( $link ,$_POST['password']);
    $sql="SELECT nome FROM $tbl_name WHERE nome='$username' and  pass='$encrypted_password'";
    $result=mysqli_query($link, $sql);
    $encrypted_password1 = md5($encrypted_password);
    // If result matched $username and $password, table row must be *AT LEAST* 1 row
    if(mysqli_num_rows($result) {
        session_start();
        $_SESSION['user'] = mysqli_fetch_assoc($result);
        $_SESSION['loggedin'] = true;
        $username1 = $_SESSION['user']; 
        header("Location: homepage.php");
    }
    else {
        header("Location: index2.php");
        die;
    } 
}
if (!(isset($_SESSION['user']) && $_SESSION['user'] != ''))
 {
    header ("Location: homepage.php");
}

  $link->close();
   ?>