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!

Updates and Other News

Wow, that was a long hiatus, wasn’t it?

I don’t always plan what I’m going to write about. Usually I just plod along in my daily grind and problems present themselves. I spend time figuring out what’s going on, and if the solution is somewhat weird, I try to explain why I thought so.

In the last twelve months or so, I’ve taken up residence at a Berlin startup called Arzttermine.de. They specialise in taking appointments for doctors online. It also lets me forget about agency work for a while and instead focus on developing a single piece of software.

…Aaand still here we are. The problem with the platform we had was that it was… old. It was built in about 14(!) days from scratch using a very old (scratch-built) CMS platform. A miracle by any stretch of investor imagination. After number of, let’s say, less-than-qualified contractors worked on it, it became a staggeringly bloated mess full of untestable spaghetti-code.

At the moment, it feels like I’m poking my head up from underwater, as the codebase is somewhat refactored and new features can be developed again without big if/else blocks wrapping method calls. I wish I worked on something interesting in the last twelve months. I like breaking down my problems into dumb little pieces and then explaining it online. I’ve been told more than a few times that my posts are helpful, and that is amazing to know.

Due to this lack of work-related creativity, I’ve started producing trite little YouTube videos that some people appear to like. If this is your thing, give it a quick look and say hi. If it isn’t, well come to Twitter and say hi anyway. I welcome the distraction from work.

– Neill

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.

Save Snapchat files (Android) – Part 1

SnapchatIf you’re using Snapchat, chances are you want to save some of the pictures and/or videos you receive. Now you can.

Edit: This post is now obsolete! Snapchat have upgraded their app, and since the time of writing, many free apps have appeared on the Google Play and Apple App Stores.

I should start with a preface: You probably shouldn’t do this. Half the fun of Snapchat is knowing it’s a one-off, and there’s a sort of “honour among thieves” type of policy between users. That being said, I do like a challenge, even if a solution does make me look creepy.

What you’ll need

  1. I assume that if you’re reading this, you have Snapchat. If you don’t, you can grab it from one of the links on their website.
  2. An Android phone. So far, this solution only applies to Android. I’m currently playing around with a solution for Apple devices.
  3. A rooted phone. I probably haven’t thought hard enough about the problem, but from what I can tell, you need to have root access for this to work.
  4. The most useful tool of all – a Terminal Emulator. There are heaps of apps out there for changing permissions and fiddling with the filesystem, but nothing is better than the ol’ terminal.

The Script

Most of what does the work is inside this shell script:

When executed (before viewing anything), the script checks the two storage locations for Snapchat (images and video), loop through the list of files, and copies the data to a safe location (a place the app can’t touch). The unusual part of the script is the use of the cat command, which we need due to some filesystem limitations within Android. Also, keep in mind that the paths above are for my device (Samsung Galaxy SIII, running Jelly Bean 4.1). You may need to update them if the script is returning errors.

Setting up the script

If you are Unix-savvy, you probably already know how to do this. You can jump down to the “how-to” section below for some notes.

If you’re a little Unix-rusty, here’s what you need to do to get this script working.

  1. First, copy/paste the script above into a new text file. Save it as whatever you like and add the extension .sh. I called mine snapchat.sh.
  2. Transfer the script onto your phone using Android File Transfer (Mac) or just in Explorer (Windows). I usually just stick it in the sdcard’s “Downloads” folder. It actually doesn’t matter, as this location is temporary anyway.
  3. Open the Terminal Emulator. First switch to the root user by running the su command.

    Then, make the internal system writable by running:

    If this step isn’t working, you can try this app instead. It’s what I use, as it offers a one-click solution.

  4. Now that you’re root, we need to move the script to a place on the system to allow us to execute it without any permission errors. Thanks to an Android limitation, this will need to be done using cat. Note: Some people appeared to be having problems copying to /etc. I’m now using /data instead to avoid any difficulties. Everything except the path is the same.

    This outputs the contents of the script into a new copy located in /data. Feel free to change this location to basically anything on the phone’s internal storage.

  5. Remove the temporary copy of the script (not essential, just tidy):

  6. Once this is done, navigate to the folder you copied the script into (on the phone’s storage), and add execute permissions using chmod.

  7. All that’s left is a bit of cleanup:

    This will remount the internal storage as read-only (as it was before).

As far as set-up is concerned, that’s (thankfully) it!

How to

Now for the best part – saving files. You will need to use Terminal Emulator (or equivalent) to do this. Be aware that you need to use su, otherwise the script won’t find the files due to permission restrictions.

  1. “Snap received!”
  2. Open Snapchat and wait until your snaps are loaded. Do not open them. I can’t stress this enough. If you open them, the script will not find them.
  3. Jump to your Terminal Emulator and run:

    This will execute the script and tell you what it does (as it’s doing it).

  4. Once that’s complete (assuming no errors), you can view your snaps as normal. A copy should have been made in the location specified by the script (in my example, this is /storage/extSdCard/snapchat/)

And that’s all there is to it! Unfortunately, this process needs to be repeated every time new snaps come in. However, in part 2, we’ll be automating the whole process using Tasker, meaning that once you open the app, your files are saved. Very sneaky.

Update: Part 2 is now available!

Note: Feel free to add comments/suggestions or point out errors in the comments section below. I will be maintaining this post.

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

Help! My photos are missing hover text!

If you’re an avid Tumblr blogger and have suddenly realised your hover text (tooltips) are missing from your photos, your day is about to get better.

Something brought to my attention recently is the lack of tooltips that appear for photos posted on Tumblr, even when a caption/description is provided using the editor.

Tumblr image uploader
The image thingamajigger from Tumblr

Code-Monkey explanation

What’s actually happening here is that Tumblr/Tiny MCE is incorrectly assigning the alt text of the image. The specification outlines the use of alt text as a replacement for the image in the case that it fails to load or if the client is, in-fact, using a screen-reader, not as a tooltip (hence “alternative text”). Browsers have been using alt text as a fallback for title text for years, and this incorrect implementation is finally catching up to developers.

The tooltip text should instead be assigned to the title attribute. This is the text that shows on mouse over.

Ok, can you fix it for me?

For the blog-(and not code-)savvy, you can add a tooltip by fixing your image tags, like so:

becomes:

I’ve noticed this behaviour most recently in Google Chrome, but I suspect other browsers will follow suit. It is in accordance with the spec, after all.

I hope this cleared things up for all you Chrome-wielding bloggers out there.

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.