note 50362 added to language.oop5.interfaces

When should you use interfaces? What are they good for? Here are two examples. 1. Interfaces are an excellent way to implement reusability. You can create a general interface for a number of situations (such as a save to/load from disk interface.) You can then implement the interface in a variety of different ways (e.g. for formats such as tab delimited ASCII, XML and a database.) You can write code that asks the object to "save itself to disk" without having to worry what that means for the object in question. One object might save itself to the database, another to an XML and you can change this behavior over time without having to rewrite the calling code. This allows you to write reusable calling code that can work for any number of different objects -- you don't need to know what kind of object it is, as long as it obeys the common interface. 2. Interfaces can also promote gradual evolution. On a recent project I had some very complicated work to do and I didn't know how to implement it. I could think of a "basic" implementation but I knew I would have to change it later. So I created interfaces in each of these cases, and created at least one "basic" implementation of the interface that was "good enough for now" even though I knew it would have to change later. When I came back to make the changes, I was able to create some new implementations of these interfaces that added the extra features I needed. Some of my classes still used the "basic" implementations, but others needed the specialized ones. I was able to add the new features to the objects themselves without rewriting the calling code in most cases. It was easy to evolve my code in this way because the changes were mostly isolated -- they didn't spread all over the place like you might expect. ---- Manual Page -- http://www.php.net/manual/en/language.oop5.interfaces.php Edit -- http://master.php.net/manage/user-notes.php?action=edit+50362 Delete: added to the manual -- http://master.php.net/manage/user-notes.php?action=delete+50362&report=yes&reason=added+to+the+manual Delete: bad code -- http://master.php.net/manage/user-notes.php?action=delete+50362&report=yes&reason=bad+code Delete: spam -- http://master.php.net/manage/user-notes.php?action=delete+50362&report=yes&reason=spam Delete: useless -- http://master.php.net/manage/user-notes.php?action=delete+50362&report=yes&reason=useless Delete: other reasons -- http://master.php.net/manage/user-notes.php?action=delete+50362&report=yes Reject -- http://master.php.net/manage/user-notes.php?action=reject+50362&report=yes Search -- http://master.php.net/manage/user-notes.php