Request for Comments: Static classes for PHP

• Version: 0.1
• Date: 2008-05-03
• Author: Lars Strojny lstrojny@php.net
• Status: in the works

Static classes are a well known construct for utility classes or stateless abstraction. C# for example has an class System.Environment to access command line options, the current directory, the name of the machine where the program is running and so on. In PHP the current practice is to use an abstract class with static methods. Static classes can act as utility containers. For such utility containers or for more complex static inheritance, static classes are a helpful tool. This is why they are proposed for PHP.

<?php
static class StaticClass
{
    public static function staticMethod()
    {
        return 'foo';
    }
}
 
abstract static class AbstractStaticClass
{
    abstract public static abstractStaticMethod();
}
 
abstract static class AbstractStaticClass2
{
    public static function staticMethod()
    {
         return 'bar';
    }
}
 
 
StaticClass::staticMethod(); // (string)'foo'
AbstractStaticClass2::staticMethod(); // Throws error, not allowed. Must be extended first

The following rules would apply for static classes:

• Declared static classes may not have non-static members
• Static methods in abstract static classes may not be called. They must be extended first
• In static classes, abstract static methods are allowed again
• Static classes may not have a constructor, destructor, dynamic interceptors or __toString()
• Static classes may not extend non-static classes
• The current behaviour of abstract classes/non-static classes with static members would not change. This is important for backwards compatibility
• __setStatic() and __getStatic() will provide functionality similiar to __get() and __set()
• Static classes cannot be instantiated
• Static classes can implement interfaces containing only static methods

• A few features missing, but initial functionality works: static-classes-002.diff

• Static classes in C#