How a Perfect PHP Pagination Works ?

Pagination is a topic that has been done to death -- dozens of articles and reference classes can be found for the management of result sets ... however (and you knew there was a "however" coming there, didn't you?) I've always been disgruntled with the current offerings to date. In this article I offer an improved solution.

Some pagination classes require parameters, such as a database resource and an SQL string or two, to be passed to the constructor. Classes that utilize this approach are lacking in flexibility - what if you require a different formatting of page numbers at the top and bottom of your pages, for example? Do you then have to modify some output function, or subclass the entire class, just to override that one method? These potential "solutions" are restrictive and don't encourage code reuse.

This tutorial is an attempt to further abstract a class for managing result pagination, thereby removing its dependencies on database connections and SQL queries. The approach I'll discuss provides a measure of flexibility, allowing the developer to create his or her very own page layouts, and simply register them with the class through the use of an object oriented design pattern known as the Strategy Design Pattern.
What Is the Strategy Design Pattern?

Consider the following: you have on your site a handful of web pages for which the results of a query are paged. Your site uses a function or class that handles the retrieval of your results and the publishing of your paged links.

This is all well and good until you decide to change the layout of the paged links on one (or all) of the pages. In doing so, you're most likely going to have to modify the method to which this responsibility was delegated.

A better solution would be to create as many layouts as you like, and dynamically choose the one you desire at runtime. The Strategy Design Pattern allows you to do this. In a nutshell, the Strategy Design Pattern is an object oriented design pattern used by a class that wants to swap behavior at run time.

Using the polymorphic capabilities of PHP, a container class (such as the Paginated class that we'll build in this article) uses an object that implements an interface, and defines concrete implementations for the methods defined in that interface.

While an interface cannot be instantiated, it can reference implementing classes. So when we create a new layout, we can let the strategy or interface within the container (the Paginated class) reference the layouts dynamically at runtime. Calls that produce the paged links will therefore produce a page that's rendered with the currently referenced layout.

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