PHP Singleton Trait: Implement the Singleton pattern as a trait

This package can implement the Singleton pattern as a trait.

It defines a trait with a function named getinstance() that creates an instance of the current class if it does not exist.

The created object is stored in static variable of the trait, so next time it is checked, the created object is returned.

The trait defines the constructor as protected and the class using the trait can override it. The entire application can get the singleton object only instance via the public static method getInstance().

When there is an attempt to clone or serialize the object, the trait throws RuntimeException.

The static property for the only instance is declared as protected and is instantiated with the static keyword to allow the access from the extended class.