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    <p>You should just not use Singletons. They're Bad Practice(tm), as they introduce global state, which makes your Code much harder to test.</p> <p>One could rewrite your example by using Inversion Of Control this way:</p> <pre><code>&lt;?php // A simple Singleton for the Application function Application() { static $instance = null; if (null === $instance) { $instance = new Application; } return $instance; } class Application { protected $someService; function __construct() { $this-&gt;someService = new SomeService($this); } function test() { echo "Good."; } } class SomeService { protected $application; function __construct(Application $app) { $this-&gt;application = $app; } function test() { $this-&gt;application-&gt;test(); } } </code></pre> <p><code>Application</code> is your Main Application's class and <code>SomeService</code> is your <code>Singleton2</code>.</p> <p>No need for private constructors, etc. here and <code>SomeService</code> gets only instantiated once, with your App (considered you only instantiate your App once).</p> <p>Repeat this with other Services you want to add to your App instance.</p> <p>Some good articles on this, which are worth reading:</p> <ol> <li><a href="http://www.potstuck.com/2009/01/08/php-dependency-injection/" rel="nofollow">http://www.potstuck.com/2009/01/08/php-dependency-injection/</a></li> <li><a href="http://fabien.potencier.org/article/11/what-is-dependency-injection" rel="nofollow">http://fabien.potencier.org/article/11/what-is-dependency-injection</a></li> </ol>
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    1. POSingleton reference and recursion in PHP
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    1. USchh
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      1. VTUpMod
    1. COWhile that is slightly better, you now have a circular reference which is still quite bad.
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      1. USigorw
    2. COI used to do such things in the past but thought that I have to use singleton for classes that are intended to be instantiated only once. Isn't that Good Practice ?
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      1. USLaurent Dinclaux
    3. COYou will create your application instance only once, but you could make the Application a singleton, so the service instance gets also only created once. The main point here is, that you should at least inject the application instance into the service via a Setter/Constructor to avoid the call to `Application::getInstance()`, which causes the recursion.
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