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HHVM Blog:
Trait and interface requirements in Hack
Jun 19, 2015 @ 09:56:23

On the HHVM blog there's a recent post looking at some of the requirements around traits and interfaces in the Hack language. More specifically, they talk about type checking with traits and how interfaces can be used to help provide extra structure.

In PHP, traits are a mechanism of code reuse that, while very powerful, are also difficult to type check both efficiently and exhaustively. In this post we’ll dive more deeply into the reasons for that and see how Hack solves those problems, allowing you to use traits in a safe way without limiting their expressiveness.

They start by talking about the main problem with PHP's handling of traits (essentially copy and paste into the current class) and how they felt Hack should "just work" in allowing type checking on these "pasted" methods too. Performance limitations prevented them from handling it how they do with other variable types, so they changed things up, using a "require extends" syntax to tell the Hack engine how to allow the checking based on an interface. There's a lot more to it than this, so be sure to read the rest of the post on how they came to that conclusion.

tagged: trait interface requirement hack require extends syntax

Link: http://hhvm.com/blog/9581/trait-and-interface-requirements-in-hack

MyTechBuilder.com:
Optional Value Control-flows in PHP using Traits and Magic-methods
Jun 18, 2015 @ 09:44:02

The MyBuilderTech.com site has a new tutorial posted talking about the use of traits and magic methods for optional value handling.

Recently I have been interested in experimenting with different ways to handle optional values. Their are many examples that exist demonstrating the use of the Maybe/Optional structure within the PHP landscape. I would instead like to focus my attention on only looking into the concept of 'orElse', which I have found to be a prominent control-flow whilst using these types of value. Typically, in an imperative mind-set we are accustom to evaluating a value, and based on its existence - defined as falsely in this regard - follow a different course of action, and by-way result.

He gives an example of where a value is checked for null and something else happens when it is. This is a common practice in PHP development, but he's more interested in other ways of handling. The first of these ways is with traits. His example shows an "OrElse" trait that can be used to perform the same evaluation but does some extra magic based on the method name called (his example is "findByIdOrElse"). If the trait method isn't for you, he also offers another possible solution around the use of composition. In this case he uses the same trait but makes it a part of its own class that's then given the object to work with (his "repository").

The post ends with one more "bonus" method for handling optional values - a simple function ("_or") that evaluates the arguments given and returns the first that's "truthy".

tagged: optional value control flow trait magicmethod function truthy

Link: http://tech.mybuilder.com/optional-value-control-flows-in-php-using-traits-and-magic-methods/

Acim.net:
Trait injection in Zend Framework 2
Dec 11, 2014 @ 11:55:56

Boban Acimovic has recently posted a tutorial showing you how to use traits in a Zend Framework 2 application to inject additional functionality into your pre-existing classes.

There are several tutorials on the Internet which explain how to use interface based dependency injection in Zend Framework 2. The idea is to make an initializer, figure out which interfaces a class implements and then inject appropriate dependencies using setters defined in the interfaces. Bad part about this is that in each class you implement such an interface you have to declare a property which would hold the injected object and also to implement the setter for it, which is defined in the interface, by the way. In order to simplify this further it is possible to write trait for each interface, but then why should not use just traits? Why do we need interfaces? Is this possible at all?

He includes some example code showing how to set up dependency injection for the traits (via a custom injector based on the "InitializerInterface") and make the autoloading easier. He shows how to add this to the provider configuration as an "initializer" and create the first example trait, a checker for data in user passwords. He then drops the functionality into a service class just by using the "use" keyword and the trait name.

tagged: trait injection zendframework2 tutorial dependencyinjection service provider

Link: http://www.acim.net/2014/11/trait-injection-in-zend-framework-2/

Qafoo Blog:
Utilize Dynamic Dispatch
Oct 16, 2014 @ 11:52:18

On the Qafoo blog today Tobias Schlitt talks about dynamic dispatch, what he calls a "fundamental concept of OOP" to help provide clean, clear interfaces in the code.

I want to use this blog post to illustrate the concept of dynamic dispatch which I use a lot recently to motivate creating clean OO structures in my trainings. In my experience, this helps people to understand why we want to write code in this way. After that I will show why traits are bad in this direction.

He explains the concept of "dynamic dispatch" by starting from the beginning...with procedural PHP code. He looks at the usual flow of this kind of application that call shared functions in a "top down" fashion. He looks at what would happen if new logging needs were introduced (use a new method? patch the current one?) and the dependencies that can be introduced because of it. With this in mind, he continues and talks about how the "dynamic dispatch" happens during the code execution, splitting the log request based on the information it's given instead of different implementations for each. He points out that using a trait doesn't allow for this abstraction and instead embeds the code into the class itself, re-introducing the original problem.

tagged: dynamic dispatch oop concept example logger trait compare

Link: http://qafoo.com/blog/072_utilize_dynamic_dispatch.html

Zumba Engineering Blog:
Incorporating Mongounit into Multi-datasource Models with Traits
Oct 31, 2013 @ 10:42:27

On the Zubma Engineering blog today Chris Saylor has written up a tutorial showing how they used traits to use multiple data sources with Mongounit, working around the single source limitations it enforces.

A while back we open sourced Mongounit, a PHPUnit extension for testing models utilizing mongodb. One key issue that we’ve discovered as we incorporate MongoDB into more of our data models is that extending Mongounit’s TestCase class limits that unit test towards Mongo only as the datasource. Since only a portion of our data is in Mongo while the remaining is in MySQL, limiting a test case to work with one datasource or another is too limiting.

They tried two other solutions first, separating out the tests by data source and manually clear the Mongo data in the tests, but both ran into problems. Instead, they opted to use traits to provide drop-in Mongo testing support as needed. It provides a simple interface to set up and tear down the needed Mongo resources - an example of which is also provided in the post. The code for the trait can be found on Github.

tagged: trait mongounit unittest database multiple source model

Link: http://engineering.zumba.com/2013/10/30/multiple-data-sources-phpunit-testing/

7PHP.com:
Auto Generate Properties Dynamically For Your Classes Using Magic Methods & Reflection
Oct 28, 2013 @ 12:57:14

Accessing private class properties via getters and setters is a pretty standard way to write your applications. Unfortunately it can be time consuming to write them for every property your class may have. On 7PHP.com Khayrattee Wasseem has a few ideas (including using PHP's own Reflection functionality) to dynamically create them.

When coding a project, at times (or most of it?) some classes might have more than 3 fields (for whatever reason it suits you). So instead of each time writing and repeating setters and getters (accessor methods), I would like to have a piece of reusable code for all my classes without me ever writing a single line of code for accessors. (‘ever’ as in ‘very very rarely’). Now, we also have to take into consideration that some fields might be only get-able or only set-able – (our re-usable piece of code should cater for this)

He shows two different methods to accomplish this kind of dynamic access, one using traits and the other using normal class inheritance. HE includes the code illustration each solution and talks a bit at the end of each section of why that method might be better than the other.

tagged: reflection getter setter private property tutorial trait inheritance

Link: http://7php.com/magic-dynamic-properties/

Cal Evans:
Managing the Verbosity of symfony’s Command Object With a Trait
Jul 15, 2013 @ 12:29:39

In this new post to his site Cal Evans goes through a simple application he's created using the Symfony Command component and some of his gotchas along the way. He shows how, using a trait, he was able to control the output of the command more effectively.

Recently I came up with a project I needed to build. Honestly, it’s one of those “not useful to anyone but me” kind of projects. I decided though that while I was at it, I wanted to learn something new. Since I’ve been a die-hard Zend guy since Zend Framework was 0.2, and more recently a Silex believer, I thought I would drop down a level form Silex and dig into symfony itself. This project is strictly a command line project. No API, no web interface, just a command and a few switches. Digging around I found SymfonyComponentConsoleCommandCommand so I decided to give it a try.

He goes through some of the work he did to pull in the needed packages and create his first command. He creates a "writeln" method to output to the console that contains his check for the verbosity level of the current command options (like "quiet" or "verbose"). He introduces the trait to add some additional handling to this output, making it easier to just drop in the "writeln" functionality in any command of his choosing.

tagged: verbosity trait symfony command silex writeln

Link: http://blog.calevans.com/2013/07/10/managing-the-verbosity-of-symfonys-command-object-with-a-trait

Josh Adell:
Interfaces and Traits: A Powerful Combo
Sep 28, 2012 @ 08:51:16

Josh Adell has a new post today looking at the "powerful combination" of using traits and interfaces in PHP applications. He shows how, despite traits not implementing the interface directly, they can be used to make other classes adhere to them simply by "using" them.

If you're not using interfaces in PHP, you are missing out on a powerful object-oriented programming feature. An interface defines how to interact with a class. By defining an interface and then implementing it, you can guarantee a "contract" for consumers of a class. Interfaces can be used across unrelated classes. And they become even more useful when combined with the new traits feature in PHP 5.4.

He illustrates with a package shipping example and uses an "Addressable" Interface to define the structure for both a Company and Users class. He includes code showing how to implement it in a more traditional "implements" way in a class, but also shows an interesting way to achieve the same thing with traits. Having a trait that follows the interface makes it easy to have a class adhere to the interface just by including the trait (or "using" it).

tagged: interface trait tutorial implement use structure

Link:

Zend Developer Zone:
Trait-like Functionality for PHP
Apr 07, 2010 @ 10:05:52

In a new tutorial posted on the Zend Developer Zone today Steve Hollis looks at something several PHP developers have said they want to seen in the language - traits - and how, until then, you can use traits now (well, sort of).

So why do we need traits, anyway? PHP is a single inheritance language, meaning that each class can only extend one other. This allows us to build logical class hierarchies which extend functionality in a "vertical" way. [...] What we need is a means of re-using code other than simple inheritance. That's where traits come in. Traits are classes containing a collection of methods, usually relating to a particular behaviour.

He shares a way that you can mimic some of the functionality that traits would give you (full code is available here) with an abstract trait class, reflection and a "superclass" that's extended to pass off the requests to the correct child object.

tagged: trait functionality tutorial mimic

Link:

Stubbles Blog:
Traits for PHP
Feb 20, 2008 @ 11:17:00

On the Stubbles blog, Frank Kleine has pointed out a proposal from Stefan Marr to include functionality for traits in PHP.

As a language construct within PHP it would be very easy to do the same, but easier to learn and to use. Beside some keyword issues (the RFC uses "use" as keyword, but this will of course conflict with namespaces) I'm wondering what this will have an impact on reflection - the RFC stays unclear about this.

A trait is a free-floating chink of functionality that, instead of being confined to a class (or file) that has to be called on to use it, exists where the developer can use it from anywhere at any time. This helps solve some of the issues with single inheritance in PHP.

tagged: trait language functionality independent proposal rfc

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