php man page for traversable

TRAVERSABLE(3)								 1							    TRAVERSABLE(3)

The Traversable interface

INTRODUCTION
	Interface to detect if a class is traversable using foreach.

	Abstract base interface that cannot be implemented alone. Instead it must be implemented by either IteratorAggregate or Iterator.

       Note

	       Internal (built-in) classes that implement this interface can be used in a foreach construct and do not need to implement Iterator-
	      Aggregate or Iterator.

       Note

	       This is an internal engine interface which cannot be implemented in PHP scripts. Either IteratorAggregate or Iterator must be  used
	      instead.	When  implementing an interface which extends Traversable, make sure to list IteratorAggregate or Iterator before its name
	      in the implements clause.

INTERFACE SYNOPSIS
       Traversable

       Traversable

	This interface has no methods, its only purpose is to be the base interface for all traversable classes.

PHP Documentation Group 													    TRAVERSABLE(3)