Static classes in PHP via abstract keyword?

Question

According to the PHP manual, a class like this:

abstract class Example {}

cannot be instantiated. If I need a class without instance, e.g. for

Answer 1

There are patterns in OO that are common and well-recognized. Using abstract in an unconventional way may cause confusion (sorry, my some examples are in Java instead of PHP):

• abstract class - a class meant to conceptualize a common ancestor, but of which actual instances are not meant to exist (e.g. shape is an abstract superclass for rectangle and triangle).
  Commonly implemented by:
  • use abstract modifier on class to prevent direct instantiation, but allow deriving from the class
• utility class - a class that does not represent an object in the solution space, but rather is a collection of useful static operations/methods, e.g. Math class in Java.
  Commonly implemented by:
  • make class non-derivable, e.g. Java uses the final modifier on class, and
  • prevent direct instantiation - provide no constructors and hide or disable any implicit or default constructors (and copy constructors)
• singleton class - a class that does represent an object in the solution space, but whose instantiation is controlled or limited, often to insure there is only one instance.
  Commonly implemented by:
  • make class non-derivable, e.g. Java uses the final modifier on class, and
  • prevent direct instantiation - provide no constructors and hide or disable any implicit or default constructors (and copy constructors), and
  • provide a specific means to acquire an instance - a static method (often getInstance()) that returns the only instance or one of the limited number of instances