What are common mistakes made by beginners when writing PHP login scripts?

Common mistakes made by beginners when writing PHP login scripts include not properly sanitizing user input, not using prepared statements to prevent SQL injection attacks, and not securely storing passwords (e.g., storing them in plain text or using weak hashing algorithms). To address these issues, it is important to sanitize user input using functions like `htmlspecialchars` or `mysqli_real_escape_string`, use prepared statements with parameterized queries to prevent SQL injection attacks, and securely store passwords using strong hashing algorithms like `password_hash`.

// Sanitize user input
$username = htmlspecialchars($_POST['username']);
$password = htmlspecialchars($_POST['password']);

// Use prepared statements with parameterized queries
$stmt = $mysqli->prepare("SELECT * FROM users WHERE username = ? AND password = ?");
$stmt->bind_param("ss", $username, $password);
$stmt->execute();
$result = $stmt->get_result();

// Securely store passwords using password_hash
$hashed_password = password_hash($password, PASSWORD_DEFAULT);