Sign up php script

if(isset($_POST['submit'])){


        $firstname = $_POST['fname'];
        $lastname = $_POST['lname'];
        $email = $_POST['email'];
        $password = $_POST['password'];

        if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
             $emailErr = "Invalid email format";
        }

    $dir = "users/$firstname";

    try{
        $sql = 'SELECT COUNT(*) FROM users WHERE email = :email AND password = :password';
        $s = $pdo->prepare($sql);
        $s->bindValue(':email', $email);
        $s->bindValue(':password', $password);
        $s->execute();

    }catch(PDOException $e){
        $error  = 'error checking if user already exists' . $e->getMessage();
        include 'error.php';
        exit();
    }

    $row = $s->fetch();


    if ($row[0] > 0) {
        $alreadExists="This user already exists";
        include 'index.php';
    }else{
            try{
            $sql = 'INSERT INTO users SET
            first_name = :first_name,
            last_name = :last_name,
            email = :email,
            password = :password';
            $s = $pdo->prepare($sql);
            $s->bindValue(':first_name', $firstname);
            $s->bindValue(':last_name', $lastname);
            $s->bindValue(':email', $email);
            $s->bindValue(':password', $password);
            $s->execute();

        If(!file_exists($dir)){
            $createfolder = mkdir("$dir", 0777);
        }

    }
    catch(PDOException $e){
        $error  = 'error adding user ' . $e->getMessage();
        include 'error.php';
        exit();
    }
    session_start();
    include 'core.php';
    }
}