True Singleton Class: PHP implementation of the singleton design pattern

In software engineering, a design pattern is a general solution to a common problem in software design. One of these design patterns is called the Singleton. It's purpose can be described quite briefly as follows:

Ensure a class has only one instance and provide a global point of access to it.

It achieves this by only creating a new instance the first time it is referenced, and thereafter it simply returns the handle to the existing instance.

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sTonClass is a base class that implements the singleton design pattern.

The class can only be instantiated using a static function that assures that there is only one object of that class.

If the class was already instantiated, it returns a reference to the previously created class object.

The class also provides functions for store, retrieving and deleting object properties.