I made a site with PHP that the user enters
I wanted to do something with cookies in PHP so that when the user enters another header is displayed

<?php
include "database/pdo_connection.php";
$error="";
$errorFild="";

if(
    isset($_POST['phone']) && $_POST['phone'] !== '' 
    && isset($_POST['password']) && $_POST['password'] !== '' 
 )
    {
if(isset($_POST['sub'])){
    $phone=$_POST['phone'];
    $password=$_POST['password'];
    $smt=$conn->prepare("SELECT `password` FROM users WHERE `phone`='$phone' ");
    $smt->execute();
    $result=$smt->fetchAll();
    if(password_verify($password,$result[0]['password'])){
        $result=$conn->prepare("SELECT * FROM users WHERE phone=? ");
        $result->bindValue(1,$phone);
        $result->execute();
        $users=$result->Fetch(PDO::FETCH_ASSOC);
        $_SESSION['id']=$users['id'];
        $_SESSION['role']=$users['role'];
        $_SESSION['phone']=$users['phone'];
        **setcookie("phone", $users['phone'], time()+89000);**
        header('location:index.php');
    }
    else{
        $error=true;
    }

}


    }
    else{
        if( !empty($_POST)){
     $errorFild =true;}
    }
?>

This is the login page code

  <li class="nav-item me-0">
              <a class="nav-link mt-3 mt-lg-0" href="/login.php">
                <i class="fa fa-sign-in ms-1"></i>
                <span>login</span>
              </a>
            </li>

            <li class="nav-item me-0">
              <a class="nav-link mt-3 mt-lg-0" href="/register.php">
                <i class="fa fa-user-plus ms-1"></i>
                <span>register</span>
              </a>
            </li>


           
            </li>

            <li class="nav-item me-0">
              <a class="nav-link mt-3 mt-lg-0" href="/codeyadproject2/logout.php">
                <i class="fa fa-sign-in ms-1"></i>
                <span>logout</span>
              </a>
            </li>

           


            <li class="nav-item me-0">
              <a class="nav-link mt-3 mt-lg-0" href="/codeyadproject2/PANEL/index.php">
                <i class="fa fa-sign-in ms-1"></i>
                <span>login to panel</span>
              </a>
            </li>

and index header

my Question:
I want him not to bring me another header when he comes in
For example, instead of logging in and registering, it should log in to the panel, or if it doesn’t log in, it won’t log in to the panel anymore
What code should I put? (with cookies)

>Solution :

Your script has a couple of issues:

• Firstly, you’re trying to use sessions, but sessions are not accessible until you call session_start().
• You’re using unprepared statements, which are vulnerable to SQL injection attacks (such attacks could lead to your entire database being deleted, or worse; leaked)
• Cookies are not necessary for the purpose of logging in.
• The fetchAll() command can be replaced with fetch() because you only need a singular record.

This is what that would look like with those things fixed:

login.php:

<?php
session_start();
include "database/pdo_connection.php";
$error = "";

if (isset($_POST['phone'], $_POST['password'], $_POST['sub'])) {
    $phone = $_POST['phone'];
    $password = $_POST['password'];
    $stmt = $conn->prepare("SELECT * FROM users WHERE `phone` = :phone");
    $stmt->bindParam(':phone', $phone);
    $stmt->execute();
    $result = $stmt->fetch();

    if ($result && password_verify($password, $result['password'])) {
        $_SESSION['id'] = $result['id'];
        $_SESSION['role'] = $result['role'];
        $_SESSION['phone'] = $result['phone'];        
    } else {
        $_SESSION['error'] = 'Your username or password was invalid';
    }
    
    header('location:index.php');
}

index.php:

<?php
session_start();

if (isset($_SESSION['error'])) {
    $errorMsg = $_SESSION['error'];
    unset($_SESSION['error']);
}
?>
<?php if (isset($errorMsg)) { ?>ERROR: <?=$errorMsg?><?php } ?>
<?php if (isset($_SESSION['phone'])) { ?>
  <h1>Welcome back, <?php echo $_SESSION['phone']; ?></h1>
<?php } else { ?>
  <h1>Welcome</h1>
<?php } ?>

(personally though I hate mixing HTML and PHP, but that should be enough to get you out of your writers block)