Design Patterns: How to create database object/connection only when needed?

Question

I\'ve a simple application, say it has some classes and an \"extra\" one that handles database requests. Currently i\'m creating the database object everytime the app is use

Answer 1

This is approximately what I use.

class Database {

    protected static $connection;

    // this could be public if you wanted to be able to get at the core database
    // set the class variable if it hasn't been done and return it
    protected function getConnection(){
        if (!isset(self::$connection)){
            self::$connection = new mysqli($args);
        }
        return self::$connection;
    }
    // proxy property get to contained object 
    public function __get($property){
        return $this->getConnection()->__get($property);
    }
    // proxy property set to contained object
    public function __set($property, $value){
        $this->getConnection()->__set($property, $value);
    }

    // proxy method calls to the contained object
    public function __call($method, $args){
        return call_user_func_array(array($this->getConnection(), $method), $args);
    }

    // proxy static method calls to the contained object
    public function __callStatic($method, $args){
        $connClass = get_class($this->getConnection());
        return call_user_func_array(array($connClass, $method), $args);
    }
}

Note it only works if there is a single database in play. If you wanted multiple different databases it would be possible to extend this but beware of late static binding in the getConnection method.