Home arrow PHP arrow Page 3 - Using Late Static Bindings in PHP 5.3

Attempting to grab an instance of an abstract registry class - PHP

PHP 5.3 introduced a number of valuable features to the popular and constantly developing language, but some of them seem less useful at first glance than they actually are. Late static bindings fall into this category. This article series shows you how to unlock the true power of LSB to work for you.

  1. Using Late Static Bindings in PHP 5.3
  2. Why late static binding is so useful
  3. Attempting to grab an instance of an abstract registry class
  4. Fixing things with late static bindings
By: Alejandro Gervasio
Rating: starstarstarstarstar / 2
May 17, 2010

print this article



Unless you perform smart unit tests with your classes (which is recommended), they may display an unexpected, erroneous behavior under certain conditions. That’s exactly the case with the array-based registry defined in the previous section, even though it seems as if it would work correctly.

To demonstrate this, below I created a simple script which attempts to grab an instance of the registry via its Singleton “getInstance()” method. Check it out:  

// include the source classes

require_once 'RegistryAbstract.php';

  require_once 'ArrayRegistry.php';



// try to grab the Singleton instance of the ArrayRegistry class

$arrayRegistry = ArrayRegistry::getInstance();



/* this is a static method call that attempts to return an instance of the abstract registry, thus throwing the following error:

Cannot instantiate abstract class RegistryAbstract in path/to/AbstractRegistry.php


That was quite a big surprise, eh? Whenever the script calls up the method in question, the PHP engine complains loudly and raises a fatal error stating that the “RegistryAbstract” class is abstract, and therefore it can’t be instantiated, even though the purpose from the very beginning was to create an object from the array registry. Well, this happened because of the implementation of the “getInstance()” method. This method resolves the called class at compiling time via the keyword “self,” which in this case always returns the abstract parent. Got the point? I hope so.

However, not all is lost with the earlier example, since late static bindings address these and other issues related to static class hierarchies by using the familiar keyword “static.” Naturally, the best way to understand how this feature works is by example, so in the following section I’m going to modify the definitions of the previous registry classes. This time, they’ll work as expected.

To see how this will be done, jump ahead and read the next few lines.

>>> More PHP Articles          >>> More By Alejandro Gervasio

blog comments powered by Disqus
escort Bursa Bursa escort Antalya eskort


- Hackers Compromise PHP Sites to Launch Attac...
- Red Hat, Zend Form OpenShift PaaS Alliance
- PHP IDE News
- BCD, Zend Extend PHP Partnership
- PHP FAQ Highlight
- PHP Creator Didn't Set Out to Create a Langu...
- PHP Trends Revealed in Zend Study
- PHP: Best Methods for Running Scheduled Jobs
- PHP Array Functions: array_change_key_case
- PHP array_combine Function
- PHP array_chunk Function
- PHP Closures as View Helpers: Lazy-Loading F...
- Using PHP Closures as View Helpers
- PHP File and Operating System Program Execut...
- PHP: Effects of Wrapping Code in Class Const...

Developer Shed Affiliates


Dev Shed Tutorial Topics: