Well, working with php is colourful at the best of times, but today i encountered a bug so big, so fundamental to the design of the language, that my face almost fell off in disbelief. In short, if you're calling a method statically in PHP 4, within the static method, the '$this' keyword will point to the calling object, as opposed to being 'null' (there should be no object context in a static method). Here's an example:

class Static
{ 
  function method()
  { 
    echo get_class($this);
  }
}

class Container
{ 
  function Container()
  { 
    Static::method();
  }
}

$Container = new Container();

The output is "Container". This example is lifted off the bug report page, in which a member of the php team declares, "This is how it is implemented, no bug." . The php object model documentation backs this up,

The $this pseudo-variable is not usually defined if the method in which it is hosted is called statically. This is not, however, a strict rule: $this is defined if a method is called statically from within another object. In this case, the value of $this is that of the calling object.

What are these guys on? There can be no rational reason for this, the only explanation i can offer up is that this is a side-effect of a deficient object model implementation in PHP 4, passed off as a "feature". Moreover, it means you can't assert that the static method is actually being called statically (remember, there's not even a 'static' keyword in php 4), like so: assert("!isset($this)"); This will fail since '$this' points to the caller object! Depressing. Fundamental.

#!/usr/bin/ruby
class Static
  def Static.method
    print this.class.name
  end
end

class Container

  def initialize

    Static.method

  end

end

container = Container.new

# ./foo.rb:4:in `method': undefined local variable or method # `this' for Static:Class (NameError)

        # from ./foo.rb:10:in `initialize'

        # from ./foo.rb:13:in `new'

        # from ./foo.rb:13