[MySQLi] Database Class

class database
{ 
    // Declare database values
    private $host = localhost;
    private $username = username;
    private $password = password;
    private $database = database;
    private $connection;

    public function __construct()
    {
        $this->connect();
    }

    public function __deconstruct()
    {
        $this->close();
    }

    /*
    Connect
    Connect to the database
    - Automatically called on load
    */
    public function connect()
    {
        // Make connection
        $this->connection = mysql_connect(
            $this->host,
            $this->username,
            $this->password
        );

        // If unable to connect throw an error
        if (!$this->connection) {
            die("Could not connect: " . mysql_error());
        }

        // If unable to connect to database throw an error
        if (!mysql_select_db($this->database)) {
            die("Could not connect to database: " . mysql_error());
        }

        // Return true on successful connection
        return true;
    }

    /*
    Close
    Close connection to the database
    - Automatically called by __deconstruct
    */
    public function close()
    {
        // Close the connection
        $close = mysql_close($this->connection);

        // If unable to close, terminate and throw error
        if (!$close) {
            die("Unable to close connection to the database");
        }

        // Return true if successful
        return true;
    }
}

    $db = new database();

class form extends database
{
/*
Form functions
*/
}

    $db->insert();

Source:
https://culttt.com/2012/05/23/how-to-connect-to-mysql-through-php