Clarification on Singleton Pattern

I'm writing some utility classes for a PHP app and a lot of them will be singletons. Found myself re-writing the same code over开发者_运维知识库 and over, and decided to make an abstract base class Singleton and subclass it. Just want to make sure I've done this correctly!

abstract class Singleton
{
    private static $instance = NULL;

    public static final function getInstance()
    {
        if(self::$instance == NULL)
            self::$instance = instantiate();

        return self::$instance;
    }

    protected abstract static function instantiate();
}

class LogHelper extends Singleton
{
    protected static final function instantiate()
    {
        return new LogHelper();
    }
}

Now, if I have done this correctly, I can call LogHelper $LOGGER = LogHelper::getInstance() from anywhere in my codebase, and get a reference to the same instance every time, yes?

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You will probably need to define your getInstance() methods as static so that you can access them without having to instantiate the class. Then, you'll use this:

$objSingleton = LogHelper::getInstance();

And, you'll probably want to define a private constructor:

private function __construct() { }

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While singletons seem like the ideal solution at first, they are not. Learn about registries and dependecy injection; they will make your life easier when you start unit testing.