Upgrading to PHP 5

Iterator and SPL Classes and Interfaces

This chapter demonstrates many classes, abstract classes, and interfaces, yet it only begins to touch on the full nature of SPL.

Table 6-3 is a quick-reference guide to the complete collection of SPL iterators, including some not mentioned in this chapter. For more information, see the SPL section of the PHP Manual at http://www.php.net/spl.

Table 6-3. Iterator and SPL classes and interfaces

Name	Type	Relationship	Description
ArrayObject	Class	Implements IteratorAggregate interface	Converts arrays and objects into iterators
ArrayIterator	Class	Implements Iterator interface	Used by ArrayObject; cannot be instantiated directly
CachingIterator	Class	Implements Iterator interface	Provides “look ahead by one” capability using hasNext( )
CachingRecursiveIterator	Class	Extends CachingIterator class; implements RecursiveIterator interface	Adds caching support to recursive iterators
DirectoryIterator	Class	Implements Iterator interface	An iterator for directory files
FilterIterator	Abstract class	Implements Iterator interface	Allows filtering of other iterators using accept( ) method
Iterator	Interface	Defines Iterator interface	Implements an iterator
IteratorAggregate	Interface	Defines IteratorAggregate interface	Allows classes to control iteration by returning iterator from getIterator( ) method
LimitIterator	Class	Implements Iterator interface	Emulates database LIMIT clause ...