Question

I’m creating a web app with various classes for things like the user, Smarty template control, etc.

I already have a database class which is all well and good, but I’m concerned about the performance of it.

Currently, in another class, I’m doing $this->db = new DB() to create a local database instance, however the database class’s __construct() function creates a new connection to the MySQL server every time I make a new DB() instance, which is obviously less than sensible. This means that each instance of all my different classes that uses the database class makes a connection to the server. I don’t have a vast amount of classes, but I only want one per page load.

This is a stripped down sample of what I have at the moment:

// Database class used by multiple other classes
class DB {
    private $dbh;

    function __construct() {
        $this->dbh = // PDO connection here
    }

    public function query($str) {
        // Do a query
    }
}

// Example class User
class User {
    private $db;    // Stores local instance of DB class.

    function __construct() {
        $this->db = new DB();    // Makes a new connection in DB::__construct()
    }

    public function login() {
        $this->db->query('SELECT * FROM users');
    }
}

I’m looking for the “best” or most common practice of doing this. I don’t want to make 10-ish separate connections for each page load.

I want to know what the best way of using and managing a DB class in my application. My four thoughts are these:

1. Would using a persistent connection to the MySQL server solve this multiple connection issue for me?
2. Should I use a static factory class and return a DB instance instead of using new DB()?
3. Is the proper solution to use an entirely static class and just do DB::query() (for example) every time I reference it?
4. I often use multiple classes in another (so we might have class Folders which requires classes User, DB and Smarty). Is it general practice to extend each class somehow?

Answer 1

If you make the variable holding the connection static, then you can check if you already established a connection. Static variables are the same across all instances of the class, so you can create 100 instances that all use the same connection. You just need to reference it statically: self::$dbh instead of $this->dbh.

class DB {
    private static $dbh = null;

    function __construct() {
        if ( is_null(self::$dbh) ) {
            self::$dbh = // PDO connection here
        }
    }
 }