How to Add Login and Signup Button in an Education Website

<nav>
  <a href="login.html" class="btn login">Login</a>
  <a href="signup.html" class="btn signup">Sign Up</a>
</nav>

.btn {
  padding: 10px 20px;
  border-radius: 5px;
  text-decoration: none;
  font-weight: bold;
}

.login {
  background-color: blue;
  color: white;
}

.signup {
  background-color: green;
  color: white;
}

<form action="login.php" method="POST">
  <label>Email:</label>
  <input type="email" name="email" required>
  <label>Password:</label>
  <input type="password" name="password" required>
  <button type="submit">Login</button>
</form>

<form action="signup.php" method="POST">
  <label>Name:</label>
  <input type="text" name="name" required>
  <label>Email:</label>
  <input type="email" name="email" required>
  <label>Password:</label>
  <input type="password" name="password" required>
  <button type="submit">Sign Up</button>
</form>

CREATE TABLE users (
  id INT AUTO_INCREMENT PRIMARY KEY,
  name VARCHAR(255),
  email VARCHAR(255) UNIQUE,
  password VARCHAR(255)
);

<?php
$conn = new mysqli("localhost", "root", "", "education_website");
if ($_SERVER["REQUEST_METHOD"] == "POST") {
  $name = $_POST["name"];
  $email = $_POST["email"];
  $password = password_hash($_POST["password"], PASSWORD_BCRYPT);

  $sql = "INSERT INTO users (name, email, password) VALUES ('$name', '$email', '$password')";
  if ($conn->query($sql) === TRUE) {
    echo "Signup successful!";
  } else {
    echo "Error: " . $conn->error;
  }
}
?>

<?php
$conn = new mysqli("localhost", "root", "", "education_website");
if ($_SERVER["REQUEST_METHOD"] == "POST") {
  $email = $_POST["email"];
  $password = $_POST["password"];

  $sql = "SELECT * FROM users WHERE email='$email'";
  $result = $conn->query($sql);

  if ($result->num_rows > 0) {
    $user = $result->fetch_assoc();
    if (password_verify($password, $user["password"])) {
      echo "Login successful!";
    } else {
      echo "Invalid password!";
    }
  } else {
    echo "User not found!";
  }
}
?>

session_start();
if (!isset($_SESSION['user_id'])) {
    header("Location: login.html");
    exit();
}