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PODatabase class design
 

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  1. PODatabase class design
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    <p>I'm creating a web app with various classes for things like the user, Smarty template control, etc.</p> <p>I already have a database class which is all well and good, but I'm concerned about the performance of it.</p> <p>Currently, in another class, I'm doing <code>$this-&gt;db = new DB()</code> to create a local database instance, however the database class's <code>__construct()</code> function creates a new connection to the MySQL server every time I make a new <code>DB()</code> 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.</p> <p>This is a stripped down sample of what I have at the moment:</p> <pre><code>// Database class used by multiple other classes class DB { private $dbh; function __construct() { $this-&gt;dbh = // PDO connection here } public function query($str) { // Do a query } } // Example class User class User { private $db; // Stores local instance of DB class. function __construct() { $this-&gt;db = new DB(); // Makes a new connection in DB::__construct() } public function login() { $this-&gt;db-&gt;query('SELECT * FROM users'); } } </code></pre> <p>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.</p> <p>I want to know what the best way of using and managing a DB class in my application. My four thoughts are these:</p> <ol> <li>Would using a persistent connection to the MySQL server solve this multiple connection issue for me? </li> <li>Should I use a static factory class and return a DB instance instead of using <code>new DB()</code>?</li> <li>Is the proper solution to use an entirely static class and just do <code>DB::query()</code> (for example) every time I reference it?</li> <li>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 <code>extend</code> each class somehow?</li> </ol>
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    1. USBojangles
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      1. USJames P.
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    1. COYou're on the right track to keep the DB as a class property... This is often done either by creating a singleton for the database whose instance is retrieved in each class needing it, or (perhaps better) by dependency injection, whereby you instantiate the DB and then pass it into the constructor as a parameter.
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      1. USMichael Berkowski
    2. COThere are a couple of good illustrations around here somewhere. If I find one I'll link it.
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      1. USMichael Berkowski
    3. CO[Here's one](http://stackoverflow.com/questions/2017911/properly-using-classes-in-other-classes-in-php) with a good accepted answer. There are others with multiple good answers..
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      1. USMichael Berkowski
 

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