login - register.php

<?php
    $conn = mysqli_connect("127.0.0.1", "root", "123123", "login");
    if(!$conn){
        echo "database connection error";
    }

    if(isset($_POST["register"])){
        $username = mysqli_real_escape_string($conn, $_POST["username"]);
        $password = mysqli_real_escape_string($conn, $_POST["password"]);
        $email = mysqli_real_escape_string($conn, $_POST["email"]);

        $password_hash = password_hash($password, PASSWORD_DEFAULT);

        mysqli_query($conn, "INSERT INTO users (username, password, email) VALUES
        ('$username', '$password_hash', '$email');");

        echo "User registered";
    }

?>

<form method="post">
    Username: <input name="username" type="text"><br>
    Password: <input name="password" type="password"><br>
    Email: <input name="email" type="email"><br>
    <button name="register" type="submit">Register</button>
</form>

<a href="index.php">Login</a>