REGISTER
________
<?php
require_once("dbconnect.php");

$error = null;

if(isset($POST['btn-register'])){
    $email = trim($_POST['email']);
    $email = strip_tags($email);
    $email = htmlentities($email, ENT_QUOTES);

    $pass = trim($_POST['password']);
    $pass = strip_tags($pass);
    $pass = htmlentities($pass, ENT_QUOTES);

    $user = trim($_POST['user']);
    $user = strip_tags($user);
    $user = htmlentities($user, ENT_QUOTES);

    $mysqli_query  = sprintf("SELECT userEmail FROM users WHERE userEmail = '$email'", mysqli_real_escape_string($db, $email));
    $conn         = $db->query($mysqli_query);

    if (strlen($pass) > 6) {
        if ($conn->num_rows <= 0) {
            $conn->close();
            $mysqli_query  = sprintf("SELECT userName FROM users WHERE userName = '$user'", mysqli_real_escape_string($db, $user));
            $conn         = $db->query($mysqli_query);
            if ($conn->num_rows <= 0) {
                $conn->close();
                $stmt = $db->prepare("INSERT INTO users (userName, userPassword, userEmail) VALUES (?, ?, ?)");
                $stmt->bind_param("sss", $user, $password, $email);
                $password = password_hash($pass, PASSWORD_BCRYPT);
                $stmt->execute();
                echo "Successfully registered";
                exit;
            }
            else {
                $error = "Username is already taken";
                echo $error;
                exit;
            }
        }
        else {
            $error = "Email is already taken";
            echo $error;
            exit;
        }
    }
    else {
        $error = "Password most be higher than 6";
        echo $error;
        exit;
    }
}
?>

LOGIN
_____

<?php
session_start();
require_once("dbconnect.php");

$error = null;

if(isset($_POST['btn-login'])) {

    $email = trim($_POST['email']);
    $email = strip_tags($email);
    $email = htmlentities($email, ENT_QUOTES);

    $pass = trim($_POST['password']);
    $pass = strip_tags($pass);
    $pass = htmlentities($pass, ENT_QUOTES);

    if(!empty($email && $pass)) {
        $stmt = $db->prepare("SELECT userId, userName, userPass FROM users WHERE userEmail = '$email'");
        $stmt->execute();
        $row = $stmt->fetch();
        $password = password_hash($pass, PASSWORD_BCRYPT);

        if($stmt->num_rows >= 0 && $row['userPass'] == $password) {
            $_SESSION['user'] = $row['userId'];
            header('Location: home.php');
        }
        else {
            $error = "Incorrect Credentials, Try again...";
            echo $error;
            exit;
        }
    }

    if(empty($email)) {
        $error = "Please enter your email address.";
        echo $error;
        exit;
    }

    elseif(!filter_var($email, FILTER_VALIDATE_EMAIL)) {
        $error = "Please enter a valid email address.";
        echo $error;
        exit;
    }

    if(empty($pass)) {
        $error = "Please enter your password.";
        echo $error;
        exit;
    }
}
?>

DBCONNECT
_________

<?php
$servername = "localhost";
$username = "root";
$password = "";
$dbname = "test";
$db = new mysqli($servername, $username, $password, $dbname);

if ($db->connect_error) {
    die("Connection failed: " . $db->connect_error);
}
?>