How can the PHP code be modified to improve the handling of user data updates, specifically in relation to login changes?

To improve the handling of user data updates, specifically in relation to login changes, we can modify the PHP code to check if the new login username provided by the user is already taken by another user in the database before allowing the update to proceed. This will help prevent conflicts and ensure data integrity. 

// Check if the new login username is already taken before updating
$new_username = $_POST['new_username'];

// Query to check if the new username is already in use
$stmt = $pdo->prepare("SELECT * FROM users WHERE username = :username");
$stmt->bindParam(':username', $new_username);
$stmt->execute();

if($stmt->rowCount() > 0) {
    echo "Username already taken. Please choose a different username.";
} else {
    // Proceed with updating the user's login information
    $user_id = $_SESSION['user_id'];
    $update_stmt = $pdo->prepare("UPDATE users SET username = :new_username WHERE id = :user_id");
    $update_stmt->bindParam(':new_username', $new_username);
    $update_stmt->bindParam(':user_id', $user_id);
    $update_stmt->execute();
    echo "Login information updated successfully.";
}

Keywords

PHP user data updates login changes data handling security

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