What's New in PHP 5 - SPL: Exceptions and Iterators (Page 3 of 4 ) PHP 5 comes with the Standard PHP Library (SPL), a collection of objects built to handle various tasks such as exception handling and object traversal (iteration). There are basically six groups of classes/interfaces available natively to the SPL. - Iterators: SPL provides built in iterators to assist in a common task - object traversal. Iterators provide a way to traverse an object’s contents without exposing the inner workings of the object to the outside world. Iterators can be built to work on any data structure and provide a standardized interface. Some of the iterator classes and interfaces available in the SPL are: Iterator, OuterIterator, RecursiveIterator, IteratorIterator, ParentIterator, SeekableIterator, NoRewindIterator, and InifiniteIterator.
Each iterator has a specific purpose and details can be found in the PHP manual.
- Directories: Two directory classes are available in the SPL: DirectoryIterator and RecursiveDirectoryIterator. These classes allow iterator based directory traversal and eliminates the need for messy directory handles.
- XML: There is one XML handling class in SPL, SimpleXMLIterator, which provides iteration over a simplexml object.
- Arrays: SPL offers something that has long been in need in PHP - ArrayObject and ArrayIterator. These object provide, as you may have guessed, an array object as well as an object to traverse the contents of an array without making assumptions on the way the array is storing it's internal data.
- Counting: The SPL interface Countable allows you to hook into the standard array function count(), meaning you can use the count() function on a user defined object and get a meaningful result by implementing the Countable interface. This is very useful for non-simple data structures.
- Exceptions: Probably the biggest feature addition via the SPL, exceptions allow graceful error handling through try/catch blocks. The Exception class is simple to extend and the SPL provides a few standard classes of exceptions for common problems, such as LogicException, BadFunctionCallException, DomainException, OutOfRangeException, and InvalidArgumentException. Error handling has been a longtime problem in PHP and has resulted in some of the ugliest code I've ever seen, particularly using the PEAR error class. Exceptions should eliminate this sort of problem in the future.
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