<?php
    class register extends database
    {
        function __construct($username, $password, $email)
        {
            $this->username = $username;
            $this->password = password_hash($password, PASSWORD_DEFAULT);
            $this->email = $email;
            $this->activation_id = $this->generateActivationId();
            $this->sender_email = 'support@url.com';
            $this->activation_link = 'http://url.com/folder/activate.php?id=' . $this->activation_id;
            $this->database = new database();
        }

        function generateActivationId()
        {
            $generator = bin2hex(random_bytes(10));
            return $generator;
        }

        function registerAccount()
        {
            $this->database->connect();
            $user_lookup = $this->database->execute_query("SELECT * FROM users WHERE username = '" . $this->username . "'");

            if (mysqli_num_rows($user_lookup) > 0)
            {
                return false;
            }
            else
            {
                $this->database->execute_query("INSERT INTO users (username, password, email, activation_id) VALUES ('" . $this->username . "', '" . $this->password . "', '" . $this->email . "', '" . $this->activation_id . "')");
                $user_lookup_comfirm = $this->database->execute_query("SELECT * FROM users WHERE username = '" . $this->username . "'");

                if (mysqli_num_rows($user_lookup_comfirm) > 0)
                {
                    $this->sendRegisterEmail();
                    return true;
                }
                else
                {
                    return false;
                }
            }
        }

        function sendRegisterEmail()
        {
            $subject = 'Registration - Activate your account';
            $message = 'Thank you for registering. Please activate your account by visiting the following site: <a href="' . $this->activation_link . '">Website link</a>';
            $headers = 'From: ' . $this->sender_email . "rn" .
                'Reply-To: ' . $this->sender_email . "rn" .
                'X-Mailer: PHP/' . phpversion();

            mail($this->email, $subject, $message, $headers);
        }
    }
?>

<?php
    class database
    {
        function __construct()
        {
            $this->dBusername = 'xxx';
            $this->dBpassword = 'xxx';
            $this->dBhost = 'localhost';
            $this->dBdatabase = 'xxx';
            $this->dBcharset = 'utf8';
        }

        function connect()
        {
            $mysqli = new mysqli($this->dBhost, $this->dBusername, $this->dBpassword, $this->dBdatabase);

            if ($mysqli->connect_errno)
            {
                $this->_mysqli = false;
            }
            else
            {
                $mysqli->set_charset($this->charset);
                $this->_mysqli = $mysqli;
            }
        }

        function execute_query($sql)
        {
            if($results = $this->_mysqli->query($sql))
            {
                return $results;
            }
            else
            {
                return false;
            }
        }
    }
?>