John Kleijn - PHP

Topological sorting of JavaScript files

nospam@example.com (John Kleijn) — Wed, 29 Dec 2010 09:46:34 +0100

Recently I'm doing a lot of ExtJS work. In complex JS app developement you'll quickly have a LOT of files to link to your HTML document. You'll want to combine and compress these files for production and link them sperate and uncompressed for testing.

The simplest solution is just listing the files in a configuration file. But managing this list is a PITA. We're developers, not clerks. So I decided this list should be auto-generated and properly sorted. Scanning the filesystem for javascript files is trivial, and I quickly decided the sort order should be determined by examining the contents, looking for class names. All files contain classes, with a JSDoc declaration of @class app.module.ClassName, so it's not hard to establish which file depends on which.

The real issue is sorting. Before long I came to the conclusion that there's no out of the box solution for the type of sorting I needed, all sort functions use QuickSort, even the ones using UDFs. On WikiPedia, I found that what I needed "resolving dependencies into an ordered list" could be accomplished using a different algorithm called "Topological sorting".

WikiPedia describes one implementation in pseudo code:

L ← Empty list that will contain the sorted elements
S ← Set of all nodes with no incoming edges
while S is non-empty do
remove a node n from S
insert n into L
for each node m with an edge e from n to m do
remove edge e from the graph
if m has no other incoming edges then
insert m into S
if graph has edges then
output error message (graph has at least one cycle)
else
output message (proposed topologically sorted order: L)

I decided to create a PHP implementation of this algorithm.

Continue reading "Topological sorting of JavaScript files"

Story: Doctrine 2 lead up

nospam@example.com (John Kleijn) — Fri, 23 Jul 2010 10:33:21 +0200

I had been waiting for PHP 5.3 for a long time, and looking at the progress for Zend Framework 2.0, I got very frustrated. But it made me keep a closer eye on the ZF Wiki, and when I encountered a proposal for Zend_Db_Mapper, I recognized many of the PoEAA patterns I had abandoned for reasons of practicality, but longed for so much. But the work was far from done, so I emailed the proposer, Benjamin Eberlei, on 19 December last year, offering my assistance. He responded..

Hello John,
I stopped to work on Zend Entity (and Db Mapper) when we realized that
it actually would end up being sort of a clone of the Doctrine 2 project,
so we joined forces and we will see some pretty neat ZF and Doctrine 1 /2
integration very soon.
you are always welcome to contribute to doctrine 2, its quite advanced
already.
greetings,
Benjamin

I was very disappointed. Zend Framework has a certain robustness, a defensiveness, that I've come to expect (although around this same time ZF started to disappoint in this regard). Doctrine, to me, was superior in functionality to Zend_Db_Table, but it definitely lacked defensiveness. It was messy. And "you can't build a palace on a pile of shit", the lesson I extracted from my experience with the SilverStripe CMS.

I responded to Benjamin expressing my disappointment and lack of faith in the quality of Doctrine. And even though he responded with assurances that Doctrine 2 was very different from Doctrine 1, I remained skeptical and disappointed.

Some months passed, and eventually I did have another look at D2, which had reached the last Alpha stage. I didn't really look at the docs, I assumed that it would be better than D1, but remained skeptical. Regardless, a bleak hope of "a better Doctrine" started to glimmer, and I started to investigate. I quickly came across this presentation by Jonathan Wage. He had me at "completely rewritten", but going on to "kill the magic", it really caught my attention. The "magic" had annoyed me greatly, as it is very inflexible, a source of unclear execution flow, and perhaps the primary source of the lack of defensiveness in D1. Going on to replace the magic with proper OO principles, I was sold. This Doctrine was indeed better, fundamentally better. There was more to the presentation, but it was just icing on the cake. The realization that it was still in alpha, tempered my enthusiasm enough to let it be.

Then I came across a project, that had the need for composite objects in a hierarchal structure, that needed to be persistent. Given the possible nesting level of these structures, I needed something that doesn't require many round trips to the database. Enter Nested Set (aka "Modified Preorder Tree Traversal"). Doctrine 1 does support that, but as it turned out, the combination of inheritance using "column aggregation" and nested set, was asking too much. This was mostly due to the poor inheritance mapping in D1. In desperation (and remembering a promise of "better support for inheritance"), I looked at the latest release of Doctrine, which turned out to be 2.0 BETA1. I was pleased the project had finally reached beta status, and started looking at the docs. I became more and more convinced that it was doable to rip out the guts of the application and replace it with D2.

This was a daunting task though, and I did underestimate it. I ended up namespacing the whole application, creating my own Nested Set implementation for use with D2, and overall just making mayor changes to the application. It put mayor stress on the deadline and myself, especially halfway through. But, the end result seemed worth it, and I am truly impressed with Doctrine 2.

Another thing I am anticipation of is Symfony 2. I never cared much for S1, but I had a look at S2 and it looks pretty good. It relies pretty heavily on DI, another prerequisite for effective Domain Driven Development. Regrettably it won't reach beta until next year. Fabien Potencier apparently coined the expression "kill the magic", and seems as impressed with D2 as I am:

And man, Doctrine 2.0 is gorgeous. Doctrine 2.0 is one of best things that's happened to PHP in a long time.

Notes about closures in PHP

nospam@example.com (John Kleijn) — Sat, 27 Mar 2010 17:47:08 +0100

When PHP 5.3 came out, I was ecstatic. Namespaces, finally! Actually some parts of the implementation were a bit disappointing, but we'll leave that for another time. In that same enthousiasm, I jumped on closures like a hungry dog on a steak. Only to find the steak to be an old shoe.

Continue reading "Notes about closures in PHP"

Virtual Proxies revisited

nospam@example.com (John Kleijn) — Thu, 25 Mar 2010 16:13:00 +0100

Of all the well known design patterns related to ORM, the Proxy pattern (or more specifically, Virtual Proxy) is perhaps the most under-appreciated (with Unit of Work Controller and Value List Handler coming in second). This may be because it's not strictly a data source pattern, and you won't find in PoEAA chapter or Core J2EE Patterns. It is actually in the GoF, which doesn't contain any data source patterns. For me personally, Virtual Proxy will always be directly associated with data loading, as that is what I first used it for in 2006, although since then I have used for other occasions where object initialization was abnormally expensive. It is a pretty versatile pattern.

In a nutshell, a Virtual Proxy is a "lazy loading" pattern that defers initialization of an object until it needed. The proxy does not contain the actual resource, but "knows how to get it". It does this by extending a subjects class while delegating to an instance of that same class, the subject. Basically this is what a Decorator does. But instead of overriding methods to add behaviour to a decorated object, it overrides them to trigger initialization of the subject (loading from the database in the case of an ORM), before delegating to the subject. Like with a decorator you'll have to override every method so that it is delegated to the subject. This makes manually writing proxies a pain.

Continue reading "Virtual Proxies revisited"

Started on a new framework

nospam@example.com (John Kleijn) — Wed, 24 Mar 2010 13:03:38 +0100

Yet again.

Actually, using bits and pieces from previous works of art and a lot of red bars that turned green eventually, it is actually already a usable framework. Which allows me to focus on the more interesting stuff that are going to set this framework apart. Starting with the data layer.

Continue reading "Started on a new framework"

Nuff Said.

nospam@example.com (John Kleijn) — Mon, 13 Apr 2009 12:41:00 +0200

function extraStatics() {
return $this->extraDBFields();
}

/**
* @deprecated 2.3 Use extraStatics()
*/
function extraDBFields() {
return array();
}

(This gem was taken from SilverStripe)

"Don't blame us, blame PHP"

nospam@example.com (John Kleijn) — Mon, 13 Apr 2009 12:11:00 +0200

At SilverStripe, they've gone through great lengths to rape the OO model (seriously, stay clear). But according to SS, their way is the right way, and PHP has it ALL WRONG. The fact that SilverStripe's codebase looks like my kitchen when the gf is out of town, is as defensive as an 80 year old Amish women in a coma, and about as structurally sound as house of cards, is ALL PHP's fault! Obviously is has nothing to with the way they are trying to use static properties. Right.

/**
* ...
*
* Note: please ensure that the static variable that you are overloading is explicitly defined on the class that
* you are extending. For example, we have added static $has_one = array() to the Member definition,
* so that we can add has_one relationships to Member with decorators.
*
* If you forget to do this, db/build won't create the new relation.
* Don't blame us, blame PHP!
*/

Adding a winky does not make it funny or right, sorry. Actually, double fail for smilies in code. Triple fail for writing the biggest piece of crap in PHP history (and that's saying a lot, MediaWiki anyone?)

SOAP server in 30 seconds

nospam@example.com (John Kleijn) — Fri, 02 Jan 2009 06:01:00 +0100

I sometimes get the feeling that some PHP developers think SOAP is hard to use. When in most cases, nothing could be further from the truth.

Continue reading "SOAP server in 30 seconds"

Unserialize vs Include, with APC or php://memory

nospam@example.com (John Kleijn) — Sun, 07 Dec 2008 04:40:00 +0100

As a follow up on my previous post, I decided it would be interesting to see what effect using the php://memory wrapper or APC would have on the results.

Continue reading "Unserialize vs Include, with APC or php://memory"

Unserialize vs Include

nospam@example.com (John Kleijn) — Sun, 07 Dec 2008 02:55:00 +0100

Cutting straight to chase, the results:

r448191@goliath:~/bench$ php bench.php 10
Total include: 0.000389575958252
Total unserialize: 0.000274181365967
r448191@goliath:~/bench$ php bench.php 100
Total include: 0.0033860206604
Total unserialize: 0.00247645378113
r448191@goliath:~/bench$ php bench.php 1000
Total include: 0.0342044830322
Total unserialize: 0.0263719558716
r448191@goliath:~/bench$ php bench.php 10000
Total include: 0.32866358757
Total unserialize: 0.25150680542
r448191@goliath:~/bench$ php bench.php 100000
Total include: 3.23683238029
Total unserialize: 2.56990027428

Continue reading "Unserialize vs Include"

Zend Framework 1.7: Zend_Db_Table still sucks

nospam@example.com (John Kleijn) — Sun, 30 Nov 2008 14:18:00 +0100

Zend Framework is now at version 1.7, adding better internationalization support, and supporting the Dijit Editor Widget. Ok, better internationalization support can only be good (since it was already more than decent), but the Editor Dijit should have been in 1.6. I gave the Dojo support in 1.6 a test drive when it was first released, only to find that it was mostly useless. Hopefully that has changed, I haven't tried it yet.

Continue reading "Zend Framework 1.7: Zend_Db_Table still sucks"

Design Patterns on PHPFreaks.com

nospam@example.com (John Kleijn) — Thu, 09 Oct 2008 16:07:00 +0200

Putting it off for forever, I have finally started writing about Design Patterns on the PHPFreaks.com site. Originally, I was planing on creating a single tutorial on all common patterns. The magnitude of task is why I kept putting it off.

Instead, I am now covering one or two patterns at the time, making for byte sized chucks for reader and writer.

Zend Framework Transform View

nospam@example.com (John Kleijn) — Wed, 30 Jul 2008 15:43:00 +0200

I implemented Transform View (XSLT) for Zend Framework. It's a relatively basic class that allows layout templates and calling Zend Framework View Helpers from XSL templates. Read on to view the class and some basic explanation.

Continue reading "Zend Framework Transform View"

OO PHP Tutorials

nospam@example.com (John Kleijn) — Sat, 07 Jun 2008 08:21:00 +0200

On my blog I assume the reader to be eloquent in OO PHP. Knowing very well this isn't the case for 70%+ of the PHP developers out there, I've started a series of tutorials on PHPFreaks.com that will give you the grand tour of OO in PHP.

Part 1 is an overview of what features PHP has to offer in respect to OOP.

http://www.phpfreaks.com/tutorial/oo-php-part-1-oop-in-full-effect

Part 2 is an introduction to some OO principles and practices.

http://www.phpfreaks.com/tutorial/oo-php-part-2-boring-oo-principles

Part 3 is an introduction to UML Class Diagrams and class relations

http://www.phpfreaks.com/tutorial/oo-php-part-3-uml-classes-and-relations

More parts to come.

A Composite Command Chain

nospam@example.com (John Kleijn) — Tue, 27 May 2008 18:36:37 +0200

My idea of fun is to combine existing patterns, producing a solution to more specialized problem than the original pattern specifications individually. I should probably get out more.

In this case, I was faced with the following problem: how to create a flexible, complex and multi-dimensional chain of Command Objects (a chain of commands and subcommands), that was executable top down over and over, without re-executing the same command twice for that chain. Operations should block the execution of their children on failure to complete. Children should be executed serial, and isolated from each others potential failure.

When faced with creating complex relations between objects of the same type, with operations to be executed on the underlying structure transparently, the Composite pattern can usually save the day. I created a mechanism to create a composite structure of any implementation of an abstract Command Object class.

Because I implemented Composite, I already had a mechanism to execute a Command and it's descendants in the order required.

Continue reading "A Composite Command Chain"