class Database {
private $_connection;
private $_host = "localhost";
private $_username = "root";
private $_password = "";
private $_database = "cmsi";

// Conect to database is private and can only be used by getConection function result is returned object of mysqli class
//can be seen in var_dump() function
private function conect() {
    //$this refers to class Database and her functions and propertys are being acsessed via -> sign
    $this->_connection = new mysqli($this->_host, $this->_username,
                                    $this->_password, $this->_database);

    // Error handling
    if(mysqli_connect_error()) {
        trigger_error("Failed to conencto to MySQL: " . mysql_connect_error(),
                      E_USER_ERROR);
    }
    return $this->_connection;

}
//Safest way to iniate conection
public function getConection(){
    return $this -> conect();
}
}


 class Category{
private $db_sql;
public function  __construct($db){
    $this->db_sql = $db;
}

public function read(){
    $conection = $this->db_sql;
    $query = "Select * from category";
    $result = $conection -> query($query);
    return $result;
   }

 }

$db = new Database();
$conection = $db->getConection();
$obj = new Category($conection);
$obj->read();