What is the Dependency Injection Container (DIC)?

If you’re coding for the web, you almost certainly have encountered frameworks that make use of the Dependency Injection Container. Incredibly useful – but what is it?

In the most simplistic way – it’s just a great big bag of stuff. That’s it. There’s nothing magical about the container, it’s simply an object that stores references to other objects. Combined with a liberal use of Interfaces, this allows for a high level of abstraction and therefore also aids in unit testing smaller code parts.

For example, if you’re injecting the entire DIC into a component, you are metaphorically handing that component a great big bag of stuff and saying “here’s what we have to work with. Ask for it by name.” The component may then access the container and all configured dependencies.

You may well now be saying “well that sounds a bit like code soup” – and you’d be right. Normally, you’d only inject the dependencies that a component requires (and not the whole bag). The major frameworks (e.g. Laravel, Symfony, Zend) feature Dependency Injection Containers and an associated service locator and dependency manager. These are no longer simply “great big bags of stuff“, but true DI systems that allow for a high level of abstraction.

For a super simple Dependency Injection Container, see Pimple (by Sensio Labs). This is a great place to get started with understanding how a system will utilise a DIC. It is super simple, and forces you to understand how things are bootstrapped and provided for your system.

For more detailed information on dependency injection, see these links:

Features image (with modifications):
Coffee Bag W” by DaveBleasdale. Licensed under CC BY 2.0

Installing Intl on PHP and MAMP

Compiling the Intl extension for PHP under MAMP is actually quite simple. I explain how and include a few solutions to “gotcha” problems along the way.

If needed, download the relevant ICU package, and extract it. Ensure your MAMP PHP binary is in your $PATH environment string. Snippet from StackOverflow:

Opening a Terminal to the extracted directory, I then compiled the code:

As I did not have autoconf, I installed it using Brew. Alternatively, you can compile it from source if you do not have Brew.

The next few steps are where I had some problems. I was getting strange errors:

fatal error: 'php.h' file not found
and
"ERROR: `phpize' failed"

Digging around, it turns out there’s a bit of a strange bug here. It can be quite simply solved by downloading/updating XCode from the App Store and symlinking the XCode SDK headers to the MAMP directory:

After this, simply install Intl using PECL:

If you’ve downloaded and installed XCode just now, you may get the error:

This is simply a MacOSX/XCode licensing issue. You can solve it by launching XCode or just typing:

to trigger the licence terms and agreements prompts. Afterwards, run the pecl install command again to install the extension.

Once that’s done, add the extension to your PHP config. In MAMP, this can be found under File > Edit Template > PHP > PHP 5.6.10. Add extension=intl.so to the list of loaded extensions.

MAMP should be restarted for this to take effect.

If you have any comments/questions, please leave them below!

Get the topmost category in WordPress

If you’re using WordPress, here’s a quick snippet of code to get the oldest ancestor (topmost parent) of a category or subcategory.

This can just go in functions.php.

The only caveat to the snippet is that it will always return only a single category, so if that’s not a problem, you should be fine.

Remove extra RSS feeds in WordPress

Here’s a WordPress snippet to remove RSS feeds for comments while keeping the main one available.

RSS Icon

RSS is super nifty. It’s a great way to keep on top of breaking news and articles from your favourite blogs and/or aggregators (I’ve got over 100 subscriptions in my feedly reader).

So it’s a wonder then that WordPress offers RSS feeds for comments on all your posts. I presume there’s a group of people who really like to track conversations, but in my experience, it’s the minority. This functionality should really be an additional (and not core) part of WordPress. If you want to prevent your site serving pointless additional RSS feeds, you’ll need to remove them from wp_head.

Removing them, however, is a two-step process. Add the following to your functions.php file:

And that’s it. The first two actions strip the RSS using remove_action with a high priority. The final add_action call tells WordPress to load our function when processing wp_head. This will go through and reinsert the main feed, leaving the comment feed out.

Congratulations! Your post conversations are now untrackable.

WordPress: Add page slug to body class (including parents!)

Are you using WordPress as a CMS? Do you want to style pages with CSS logically? You might want to try this.

By default, WordPress will inject the page and its ID into the body class. That’s great if you’re only running a single install, or if you really really don’t care what your CSS looks like.

Let’s face it – you care. Otherwise, you wouldn’t be here. Here’s a snippet that will inject the current page’s slug and all slugs of its parents into the body class of your HTML.

Add this to functions.php

And that’s it! You can then start chaining together page classes to target little overrides that your clients are probably hassling you about.

Help! register_activation_hook isn’t working!

If you’re developing a plugin, chances are you’ve been caught out by the WordPress activation/deactivation hooks.

I’ve been working on an Instagram plugin for WordPress, and in doing so have needed to use the functions register_activation_hook and register_deactivation_hook.

However, I – like many others, it seems – can’t get the hooked functions to execute. They simply don’t fire. To illustrate the problem, here’s an example from the code:

I would fully expect the system to execute the functions hooked within the constructor. Had that been the case, I wouldn’t have lost a day debugging a non-existant problem.

Finding a solution

Of course, everyone’s setup is different. There were many suggestions for fixing the problem. For the sake of usefulness, here’s the other major suggestion:

Your global variables aren’t global

If (like me), your plugin is a global, you actually need to explicitly define it as such with the global keyword. For example, the snippet

should instead by written this way:

Why? Well, for this, we need to consider how the plugin has its code loaded. After installation, your plugin has its code included “normally” with standard includes. This creates the global scope that you would expect. However, when you register a function with register_(de)activation_hook, it is called from within another function’s scope, effectively hiding your non-explicit globals.

Confused? Consider the plugin example from earlier. The variable $my_instagram is declared in the global scope, with global visibility. When your code executes, your plugin is included at the same scope, meaning you will have access to the variable (as they share the same suitably-high scope). Due to the way the hook/filter system in WordPress works, your activation/deactivation hooks are executed within a localised (not global) scope.

Screen beans - the only thing worse than scope.
Screen beans – the only thing worse than scope.

This scope-confusion applies to all functions created using create_function, or (in our specific example), functions called with call_user_func (and call_user_func_array). These functions have their own scope and are thus shielded from the cheap-and-nasty pile of implicit “globals” that haven’t been properly declared as such.

You can find a suitably more technical (and probably correct) write-up at the WordPress Codex page for register_activation_hook.

tl;dr: Explicitly declare your globals if you want them to work everywhere.

Ok, that’s great, but what’s the answer?

After having accidentally (and rather unwillingly) been given a very rough refresher on scope, I found that this was not my problem at all. Even running proxy functions (which eliminates scope issues) failed to call the functions specified in the hook.

After much trial and error (and I mean much), I found that the paths within register_(de)activation_hook were not matching the path found in plugin_dir_path. In fact, __FILE__ was returning a completely different path.

The problem? I had symlinked the theme directory in my install, meaning that __FILE__ returned a different path to plugin_dir_path. This is especially important, as the file path specified by the first parameter of register_(de)activation_hook is included before the function specified by the second parameter is called. So, if the path in the first parameter is wrong, you probably aren’t going to be executing many functions today.

The Fix

This is always my favourite part. To fix the symlinking problem, you just have to be very specific when you’re asking WordPress to execute a hook for you.

Fixing the first example, we get:

The most important changes occur on lines 1, 16, and 17. The first line fixes the definition by manually specifying the path using the base plugin directory (instead of an automagic WordPress search). Lines 16 and 17 specify the main plugin file itself as the path (instead of relying on __FILE__).

This allowed WordPress to find the plugin files without a hitch, which is especially important in the installation/uninstallation phases.

Moral of the story? Check your paths first.

Paths

Pink Ribbon Breakfast

I don’t normally plug work that I do in my daily grind, but this one is for super-great cause. Instead of our usual advertising selves, we’re using our powers for good and completely upgrading the National Breast Cancer Foundation‘s Pink Ribbon Breakfast site. Their goal is to have 0 deaths by 2030, which is a pretty nice goal all-round.

We built the site using Zend Framework, CSS3, and a healthy dose of jQuery-inspired Javascript.

Jump over to the site and check out our relatively-quiet first phase launch while we get ready for the donation-crazy second phase. And be sure to visit the donate link if you know someone with breasts.

Using a single controller in Zend Framework

Are you using Zend? Do you have only a core controller and don’t need extraneous URL parameters? Try this.

Most of the time, I am using Zend Framework to its (mostly) full capacity. Models, Controllers, View Helpers – the whole box-and-dice. However, there has been several occasions where I’ve only needed a single controller serving up mostly static pages, or pages leveraging an external service.

The biggest problem that arises in this case when using the default Zend Router, is that action names are treated as controller names. I don’t know about you, but I personally hate seeing http://example.com/index/my-action when what I actually want to see is http://example.com/my-action.

Here’s a nice way to completely tidy up all your actions, serving them from a single controller. (I use a Bootstrap file to initialise my application):

This basically says that my first parameter is always going to be an action name, and everything else is to be parsed as normal. I set request defaults in the array. In this case, the default controller is “index”. This allows everything to be passed straight through to my IndexController.

Addtionally, if you are using modules and want to retain routing for these also (for example, a one-controller site with an admin module), you can add this route rule to your system:

This says that anything starting with “admin” needs to be routed to the admin module, and the rest of the URL is to be parsed as normal.

That’s it! This will allow you to route all requests to a single controller for the front-end, and still maintain a complete module for the administration on the back-end.

Hopefully this cleared up some things for others, as I found the Zend Framework documentation to be quite dismal.

Using memcache and Zend_Cache

Probably one of the more useful things you can do with memcache is drop it into Zend Framework. Here’s how I did that.

Following on from the previous post, here is an example of how you can set up memcache to serve as a cache for your Zend project.

I like to use the method style of bootstrapping my application, so here’s the function that builds the cache for me.

Originally, I was getting the “Memcache::addServer function expects at most 6 parameters, 8 given” warning. To force Zend to play nice with memcache (and send the right parameter count), you need to make sure you have the compatibility option set to true in the backend options array.

Here’s an example on how to use:

Hope this helps in getting started with Zend_Cache (even on a technology as old as memcache).

Enabling memcache under MAMP

I know the tech is a bit old, but sometimes you need to make do with the tools you’ve been given. Here’s how I enabled memcache under MAMP.

First, grab the precompiled binary file (memcache.so) from here. There were no problems using this on Snow Leopard (for me, at least).

Second, copy the file to your MAMP extensions directory. You should be able to find it here: /Applications/MAMP/bin/php5/lib/php/extensions/no-debug-non-zts-[date].

Next, you’ll need to enable the extension in MAMP. Switch it off, then open up php5.ini by going to File > Edit Template > PHP5 php.ini

Find the extensions section (about line 540 or so) and add this line to the list of extensions:

Once that’s done, save php.ini and reboot MAMP. You should be able to see an entry for memcache when opening your phpinfo page.