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Ian Cambridge:
Code Review: Single Responsibility Principle
Feb 23, 2017 @ 13:24:05

Ian Cambridge has put together a new post for his site focusing on the Single Responsibility Principle, one of the more well-known (and well understood) parts of the SOLID design principles.

Single Responsibility Principle (SRP) is probably one of the most well-known principles from SOLID. At its core is a desire to prevent classes from becoming overwhelming and bloated. While enabling the ability to change how a single thing works by only changing a single class. So the benefits of SRP are that you have an easier codebase to maintain since classes are less complex and when you wish to change something you only have to change a single class. In this blog, I will go through some ways to try and help avoid breaching SRP while doing code review.

He gives two examples and the code they might contain, breaking the SRP mentality. The first is a "manager" (or service) class that, while good in principle, usually ends up performing way too many operations than it should. The second is a "from usage" instance where the return of one method is being used as a parameter for another method in the same class. For each he talks about the problem with the current implementation and offers a suggestion or two of things to fix to make it adhere more to SRP ideals.

tagged: singleresponsibilityprinciple srp solid example code review

Link: http://blog.humblyarrogant.io/post/2017-02-21-code-review-single-responsibility-principle/

Patrick Louys:
The Open/Closed Principle
Dec 14, 2016 @ 12:12:33

Patrick Louys has written up a new post to his site that gets into detail about one of the SOLID development principles - the Open/Closed Principle - and how it can be applied in PHP.

I am a big proponent of the SOLID principles. But one of the principles - the open/closed principle - is often misunderstood. [...] Bertrand Meyer stated it first in his book "Object-Oriented Software Construction" in 1988. The problem with it is that some people see the word extension and they think that it is talking about inheritance (because PHP uses the extend keyword for inheritance).

He goes on to talk about a comment from Reddit and uses it as an illustration about the "extension" misconception and the commentor advocating against dependency injection. He then gets into some code showing a "Logger" class that writes to the filesystem and trying to extend it to add functionality. He covers how using a dependency injection container can help some of the inheritance issues (using a "base" class) but ultimately steps back to provide another solution. The re-applies both the open/closed principle and dependency injection to create a system where the "base" Logger class is a dependency rather than a parent class.

tagged: openclosed solid principle dependencyinjection application inheritance

Link: http://patrick.louys.ch/2016/12/11/open-closed-principle/

Sarfraz Ahmed:
Coding to Interface
Dec 29, 2015 @ 09:27:48

On his Code in PHP site *Sarfraz Ahmed * has a post talking about coding to interfaces, how its done and why he thinks it's an essential part of any application.

One of the nicest things you can add to your programming skills is coding to interface.

One of the nicest things you can add to your programming skills is coding to interface. One of the five principles of S.O.L.I.D is Dependency inversion principle which states: [...] High-level modules should not depend on low-level modules. Both should depend on abstractions [and] abstractions should not depend on details. Details should depend on abstractions.

He elaborates on this "pretty formal definition" with an example MySQL wrapper class used in a User class, making them tightly coupled to each other. He also points out the same with a `UserController. As a solution to this tight coupling problem, he suggests using dependency injection (inversion of control) to pass in instances of the classes rather than creating them internally. This still couples them, though a bit more loosely, so he suggests using an interface for the dependency instead of a concrete class. This way any number of potential classes could be passed in and the class internally knows how to use them.

tagged: code interface dependency injection ioc solid principles objectoriented coupling

Link: http://codeinphp.github.io/post/coding-to-interface/

ThePHP.cc:
Dependencies in Disguise
Sep 28, 2015 @ 08:48:27

On the PHP.cc's site has an article that looks at dependencies in disguise based on a "workshop" one of their members, Stefan Priebsch, gave at the recent Bulgaria PHP Conference.

Yesterday I gave a presentation at the [Bulgaria PHP Conference](https://thephp.cc/dates/2015/09/bulgaria-php-conference) (a great event, by the way). Following an [ad-hoc workshop](https://twitter.com/s_bergmann/status/647732967087939584) that I gave as part of the hallway track and an entertaining hackathon, I decided it was too late to join the party and went back to the hotel with some other speakers. Checking out how the day was reflected in social media, I contributed a few more tweets to a [conversation](https://twitter.com/tim_bezhashvyly/status/647861115721003008) that had started earlier in the day ([here](https://thephp.cc/dates/2015/09/bulgaria-php-conference/solid-mvc) are the slides of my talk that people are referring to). I am writing this to clarify my point, and help everybody to understand better.

He talks about dependency injection as a best practice that's followed in libraries all over the PHP ecosystem, making it easier to work with objects and their needs. Sometimes this means using a dependency injection container and others it's just constructor/method injection. He talks about how these objects are build in factory methods and recommends making one factory but points out that this only really works when all the objects you need are known up front. However, he gives several (code) examples of places where this could be difficult and how some are using service locators to solve the problem. He points out, however, that this then expands the API of the application out way too far, opening it up to objects all across the application when there may be no need. This is where the hidden dependencies can come in, things masked behind the use of a single service locator. He recommends solving the issue with more customized locators, as in his example of routing locator used to handle dependencies for a POST HTTP request.

tagged: dependency disguise injection service locator bestpractice solid development

Link: https://thephp.cc/news/2015/09/dependencies-in-disguise

Scotch.io:
S.O.L.I.D: The First 5 Principles of Object Oriented Design
Mar 19, 2015 @ 10:30:47

On Scotch.io today they've posted a tutorial about SOLID, the "first five principles of object oriented design". SOLID is an acronym made from the first letter of several principles that can help make your OOP code well-architected and easier to test.

S.O.L.I.D is an acronym for the first five object-oriented design(OOD) principles by Robert C. Martin, popularly known as Uncle Bob. These principles, when combined together, make it easy for a programmer to develop software that are easy to maintain and extend. They also make it easy for developers to avoid code smells, easily refactor code, and are also a part of the agile or adaptive software development. Note: this is just a simple “welcome to S.O.L.I.D” article, it simply sheds light on what S.O.L.I.D is.

They start with a basic overview of what the letters in SOLID stand for and then work through each, providing basic code examples to help make the point clearer.

tagged: solid oop design principles introduction objectoriented

Link: https://scotch.io/bar-talk/s-o-l-i-d-the-first-five-principles-of-object-oriented-design

Three Devs & A Maybe Podcast:
Episode #56: The SOLID Podcast
Jan 29, 2015 @ 12:20:03

In the latest show from the Three Devs & A Maybe podcast hosts Michael Budd, Fraser Hart, Lewis Cains and Edd Mann talk about a wide range of topics with a focus on the SOLID development principles.

This week we have a three developer podcast with discussion on a host of topics. We kick off with how Fraser has enjoyed building his first bonus slot game, written entirely in JavaScript and HTML5. Preprocessors are a huge part of the JavaScript ecosystem at this time, with so many to choose from we discuss a couple of the more popular ones. This leads on to Photoshop discussion, ReactJS, the cool features present in ES6 and how you can use them today with transpilers. Following this we move on to the SOLID principles, the overuse of inheritance, technical debt and the concept of Over-DRY vs. Software Value. This then takes us on to a strange 'rubber duck' example Edd conjured up to help try and explain the Liskov substitution and Interface segregation principles. Finally, we discuss Edd's media server setup and how he has got it to a staged that he is finally happy with it.

Other topics include things like:

You can listen to the latest show either through the in-page audio player or by downloading the mp3 of the episode. Also, be sure to subscribe to their feed of you enjoy the show!

tagged: threedevsandamaybe podcast ep56 solid development principles

Link: http://threedevsandamaybe.com/the-solid-podcast/

Anthony Ferrara:
A Beginner's Guide To MVC For The Web
Nov 24, 2014 @ 10:42:41

Anthony Ferrara has posted what he calls a beginners guide to MVC for the web, a tutorial that introduces to you the basic concepts behind the Model-View-Controller design pattern and how it should fit in with the SOLID design principles.

There are a bunch of guides out there that claim to be a guide to MVC. It's almost like writing your own framework in that it's "one of those things" that everyone does. I realized that I never wrote my "beginners guide to MVC". So I've decided to do exactly that. Here's my "beginners guide to MVC for the web".

He starts with his first lesson, his most important one really - you don't need "MVC" (the concept, not the pattern...he notes them differently). He then gets into what the MVC pattern actually is and describes each piece and how they fit together. Following that, he talks about "MVC" as a concept and how it's different from MVC, the design pattern (hint: the pattern describes one implementation of the MVC ideals). He talks about the role of state in the MVC structure and how the implementation of the MVC idea is slightly different in the various "MVC frameworks" out there.

There is a very useful lesson that MVC brings: Separation Of Concerns. Meaning that you should separate different responsibilities into different sections of your application. Separation of Concerns is a necessary step in dealing with Abstraction. Instead of latching on to MVC, latch on to abstraction. Latch on to separation of concerns. Latch on to architecture. There are far better ways to architect and abstract user interaction for server-based applications than MVC.
tagged: beginner guide mvc modelviewcontroller designpattern concept solid abstraction

Link: http://blog.ircmaxell.com/2014/11/a-beginners-guide-to-mvc-for-web.html

SitePoint PHP Blog:
Practical OOP: Building a Quiz App – Bootstrapping
Nov 14, 2014 @ 13:44:09

The SitePoint PHP blog has kicked off a new series of posts today with the first tutorial about building an application with OOP and the Slim framework. In this starting article they focus in on bootstrapping the application and introducing some of the basics behind MVC and OOP.

At a certain point of my development as a PHP programmer, I was building MVC applications by-the-book, without understanding the ins-and-outs. I did what I was told: fat model, thin controller. Don’t put logic in your views. What I didn’t understand was how to create a cohesive application structure that allowed me to express my business ideas as maintainable code, nor did I understand how to really separate my concerns into tight layers without leaking low-level logic into higher layers. I’d heard about SOLID principles, but applying them to a web app was a mystery. In this series, we’ll build a quiz application using these concepts. We’ll separate the application into layers, allowing us to substitute components: for example, it’ll be a breeze to switch from MongoDB to MySQL, or from a web interface to a command-line interface.

They start off with a bit about why "MVC is not enough" and how they'll be applying domain modeling as a part of the application. There's also a brief mention of the concept of a service layer and how it will fit into the overall structure. Then it's on to the code: getting Slim installed (via Composer) and starting in on the interface/service classes for the Quiz. They walk you through entity creation for the Quiz and Question instances and a mapper to tie them together.

tagged: practical oop tutorial series part1 bootstrap slimframework solid mvc

Link: http://www.sitepoint.com/practical-oop-building-quiz-app-bootstrapping/

Gonzalo Ayuso:
Building a Pimple/Container from a YAML file
Sep 29, 2014 @ 10:54:10

In a recent post to his site Gonzalo Ayuso shows how to create a Pimple container (a dependency injection container) from a YAML configuration definition using a simple handler already included in Pimple.

[In a conversation with Máximo Cuadros about Dependency Injection Containers] I said that I prefer Symfony´s DIC instead of Pimple, mainly because its configuration with YAML (or even xml) files. But In fact we can customise Pimple/Containers with YAML files in a similar way than we do it with Symfony’s DIC. In this example we’re going to see one way to do it.

While Pimple does come with the "Container" functionality to make this happen, Gonzalo points out that using it this way violates several of the SOLID design principles. Instead, he offers an alternate solution - using the Config component from Symfony to handle the creation of the container using an already established YAML format. He includes an example YAML configuration structure, the matching Pimple code for it and a code sample showing how the YAML is parsed into the same result. You can find the code on his GitHub account if you're interested in the full structure.

tagged: pimple symfony container solid config yaml dependencyinjection

Link: http://gonzalo123.com/2014/09/29/building-a-pimplecontainer-from-a-yaml-file/

Wojciech Sznapka:
Type Hinting is important
Jun 12, 2014 @ 09:41:51

In his latest post Wojciech Sznapka reminds us that type hinting is important in your PHP applications and can help provide more structure and better overall code practices.

One of my favorite PHP interview questions, is: what is Type Hinting and why it’s important? Putting definition in one sentence, Type Hinting is a way to define type of parameter in function signature and it’s a sine qua non to leverage polymorphism. [...] So given the fact, that Type Hinting is optional and we don’t need to specify types of parameters passed to the method – why bother? Answer is easy: well prepared method signatures defines your model and are part of the “contract” that your code reveals to its consumers. It also prevents many silly errors and keeps codebase clean and coherent.

He talks about the best practices on using type hinting including where to put them (in an interface or base class or child class?) and some of the pros and cons of each. He also points out that some practices around type hinting, like overriding the hint and calling the method with unexpected/variable input, should be avoided (see the L in SOLID).

tagged: typehint importance bestpractice liskov substitution principle solid

Link: http://blog.sznapka.pl/type-hinting-is-important