Archive for the ‘Programming’ Category

Recently I wrote about the Flight PHP micro-framework. One of the challenges I ran into when launching one of our sites in it was that we had some database information that needed to be pulled out in the layout.

It was the same information on every page so it didn’t make sense to pass it in as a variable as this would have meant using the same code on every route to do the same thing. Instead, it was simpler to create a view helper which would pull out the information needed.

class Helper {

	public static function menuTags () {
		$tagModel = Flight::tagModel();
		return $tagModel->findDistinct();
	}

}

Nothing fancy here, just a static method on a class which hooks into one of the model classes I has already registered with Flight and returns the result. I then just needed to reference this from the layout view.

<?php foreach (Helper::menuTags() as $tag) { ?>
<?=htmlspecialchars($tag["tag"])?>
<?php } ?>

Now it appears on every page without me having to pass it in as a variable.

Flight is another micro framework written in PHP and bills itself as being extensively extensible.

Like other such frameworks, you begin (and arguably end) by creating a series of routes and adding closures to those routes that present the actions and outputs of said route. The quintessential example being as follows.

Flight::route('/hello', function(){
	echo 'Hello, World!';
});

The routing works really well using the simple format that allows you to name and route and add a regular expression match in one simple statement.

Flight::route('/article/@id:[0-9]+'

You don’t have to use closures either – any callable object can be used, so you can write a separate function and call it from multiple routes – useful if you have multiple, entirely separate patterns to match where it doesn’t make sense to do it all in one regular expression.

Flight has a simple built-in views system which allows you to render a view (which just uses PHP files to keep things simple) and pass an associative array of variables in which then translate to variables which you can use in the view. Layouts are also supported.

Its real power though is in how you can extend it. You can easily write your own classes and call them into your Flight methods using its register function.

Flight::register('db', 'Database');
$db = Flight::db();

This doesn’t just apply to new classes – you have override the Flight classes with your own if you wish to as well. Flight goes far deeper though, allowing you to do what it describes as filtering, a system which allows you to insert hooks before and after functions.

Flight is a great little framework, and one to rival Silex.

The Symfony2 framework comes with a really nice validation library and on top of the built in constraints that you can use you also have the ability to add your own custom constraints to perform any other validation checks you need to do.

The Cookbook has an article on how to create such a custom constraint, but unfortunately, as has happened a few times with the Symfony2 documentation, it misses out some fundamental and sometimes rather obscure step in order to get it working.

The problem is, it doesn’t tell you where to put the files. That leaves two options – either you have somewhere they need to be in order for Symfony to find them, or you need to fell Symfony where they are.

After hours of digging around, we eventually found the answer – in your validation.yml file you need to register the namespace and then reference that name when you call the validation rules.

Start by registering the namespace at the top of your validation.yml file.

namespaces:
  myValidator: Acme\ExampleBundle\Validator\

Lets say you have added a custom validation constraint called Postcode. When you want to invoke that from your validation rules, you need to reference the namespace you have just created.

postcode:
    - myValidator:Postcode: ~

You can then use this namespace with your custom validation rules, place them in the appropriate directory (in this case src/ExampleBundle/Validator, but you can store them somewhere else if you change the namespace – remember that Symfony2 will extract the path from the namespace).

Last month, I went to a talk by Richard McIntyre on “The Future of PHP”.

Turns out, it’s JavaScript.

More and more these days, web applications are being developed with fat front end clients loaded with JavaScript, and the server-side processing is primarily used for data processing and APIs. So we’re seeing a shift from PHP being used as a somewhat front-end technology to merely (I say merely, there is a lot of work to do it) delivering the content in a format the JavaScript front end can consume.

Perhaps this is why we’ve seen a rise in the number of microframeworks, such as Silex, that I recently blogged about.

I think the overriding message I took away from the talk though is that they’re inventing development platforms faster than I can learn them! I’ve already got a large list of technologies and libraries I need to review and I think I came away from this talk with another half a dozen!

Really enjoyed the talk though, and if you’re interested in PHP and in the Leeds area you should definitely check out the Leeds PHP User Group who host such events on a monthly basis.

Silex is a PHP microframework based on Symfony2 components.

With the shift in recent years to leveraging more JavaScript and front-end code in fat clients, a lot of server-side processing has been reduced to simple data relay and APIs. As a result, there have been a number of microframeworks arisen, which allow you to serve out content in a really simple and easy way.

One of the most popular is Sinatra, a micro-framework for Ruby, which is what we built Village Chief on. Indeed, Silex is inspired by Sinatra, but is PHP-based and uses some of the great components that can be found in the Symfony2 framework.

As you would expect from a microframework, it’s really easy to get started.

<?php
require_once __DIR__.'/../vendor/autoload.php';

$app = new Silex\Application();

$app->get('/hello/{name}', function ($name) use ($app) {
    return 'Hello '.$app->escape($name);
});

$app->run();

It relies heavily on Composer, a PHP dependency manager. This is a bit of a pain if you’re not already using Composer as it means you have to have yet another piece of software on your computer, but unfortunately, you’re somewhat railroaded into it as there is virtually no documentation on how to install things like Twig without it. Luckily, once you have it, it does make things easy and pain-free, so it’s probably worth going through the initial setup.

Once you’re up and running, it’s a snap to add content. We recently re-launched Maze Finance and the entire process of getting Silex up and running and migrating our existing website into it took less than two hours!

Recently, I was trying to catch an exception that was raised when someone entered an invalid date string. Every time I tried it however, it would continue to throw the standard Symfony2 error information, rather than executing my catch block.

try {
    $date = new \DateTime($str);
    return $this->setDateOfWork($date);
} catch (Exception $e) {
    return false;
}

After a good thirty minutes of being puzzled, we eventually worked out what it was – because we were working within a namespace, we needed to call the Exception object, which is after all just another object, from the global namespace.

try {
    $date = new \DateTime($str);
    return $this->setDateOfWork($date);
} catch (\Exception $e) {
    return false;
}

This applies to any other types of Exceptions you’re trying to catch too – make sure you’re in the correct namespace!

Drupal is a great PHP-based CMS (content management system), but its true power is only unleashed when you use the modules system. Out of the box, Drupal provides basic functionality for creating and publishing content with additional functionality that can be added by installing modules, you have a far more powerful system.

In fact, most of the core functionality of Drupal is provided via modules as well. Drupal ships with a series of “core” modules which, should you wish to, you can disable. So if you don’t want the menu system, search, taxonomy or the help system, you can turn all of these off.

Beyond that though, Drupal can be extended significantly thanks to its reach ecosystem of modules (or plugins if you will) that provide significantly more functionality than the core system ships with. While you’ll need to find the right modules to match your needs, there are several that are considered the staple diet of Drupal developers.

Chaos Tool Suite
It may not look like anything special to get started with, but CT Tools provides an expensive range of APIs and systems which make developing with Drupal easier. It’s a platform to use when developing your own modules but also serves as a dependency for many other modules.

Views
The most installed module of any on the Drupal website, and it’s easy to understand why. Views is an incredibly powerful module which allows you to create custom pages that do various tasks – such as listing out a content type, sorting things a certain way, creating archives and many other tasks.

Entity Reference
At some point you will probably want to reference one entity to another. For example, on the Know Leeds website we have places and we have restaurant reviews. For each restaurant review we write, we want that to be linked to a certain restaurant (a place), and we do this with Entity Reference.

Pathauto
If you think you’re getting an exciting Greek named module, think again – it’s just the words path and auto put together. But it’s still a very useful module as it automatically creates friendly URLs without you having to type something in.

By default, Drupal won’t create a node reference for an article, it will just use the ID. You can override this by typing in something like article-title, but Pathauto will do this automatically. It’s good to install this from the start as it allows you to set up patterns for articles, categories and other systems so that you have uniform URLs across your site.

CAPTCHA and reCAPTCHA
reCAPTCHA is a fantastic took that stops spam and helps translate books at the same time. Using these two modules you can add reCAPTCHA to your site to stop spam bots registering accounts.

Taxonomy menu
This allows you to build an automatic menu out of a taxonomy set. So if you have categories as part of your taxonomy and you want to create a menu that automatically lists each category, this module will do it.

Drupal is probably the best PHP-based CMS (content management system) on the market today. However, because it has a somewhat steeper learning curve than other systems, where you can just install and start creating content, it is easy to get frustrated with it and give up.

However, a short amount of time getting your head round the basics should be enough to show you that Drupal has some really powerful features which make it a far better CMS than those that simply allow you to drop text into pages.

We used Drupal to build Know Leeds and it allowed us to quickly and easily put together a functional site that allowed the non-technical contributors to get to grips with the system.

Content types
Because most people are familiar with WordPress, I’m going to use that as a comparison throughout this article. If you’re not familiar with WordPress, don’t worry, because most, if not all of the terms used are generic concepts that you will be able to understand anyway.

In WordPress, you have two types of content – posts and pages. Posts are the bread and butter of what was traditionally a blogging only system. Pages, are similar, but are static and don’t go into the date-based archives.

In Drupal, you get to define your own content types. It comes pre-configured with an article (similar to a post) and static page content types, but where you go from there is up to you. There are two good examples of where we used this in Know Leeds.

Firstly, we added a content type for “Restaurant Review”. This is similar to the Article content type, but we wanted to add some additional fields to Restaurant Review that didn’t want to be in Article – a star rating and a categorisation of what type of food the restaurant served.

Secondly, we added a content type for “Place”. We offer listings of local bars, clubs and restaurants on the website and if you think about it, an entry for one of these is basically just a piece of content. But with different needs than an article – we need address, phone number, email address, etc. So we created a custom content type for that too.

Fields
As I discussed with our custom content types, we wanted to customise the field types on our content types. In WordPress there are a number of fields – title, body, published date, categories, etc. In Drupal, you have the same thing, but you can create your own fields and match them to each content type.

So for the Restaurant Review content type we added a star rating field. This allows the editor to enter a numeric value between one and five. We also added a Cuisine content type which allows them to pick what kind of food it is. This works just like the WordPress categories system, except we can have multiple types of categories and we can pick which content types they apply to!

Taxonomy
In WordPress, there are two types of taxonomy – categories and tags. In Drupal, surprisingly enough, you can define your own. As I’ve already discussed, we created a Cuisine taxonomy and added a list of different terms (or categories if you will) such as French, Italian and Steak House.

Drupal allows you to create as many different categorisation systems as you wish and apply them to the content types as appropriate. We only wanted Cuisine to apply to the Restaurant Review content type for example, but Category might apply to both Article and Restaurant Review.

Blocks
Units of content which can be placed somewhere in your layout are called Blocks. The nearest equivalent to this in WordPress is the “widgets” system where you can drop widgets in and out of the sidebar.

Drupal comes with some standard blocks such as user login and search form, and many of the modules you can add into Drupal will add some blocks too – adding the forum module will add an “active forum topics” block for example. Of course, you can create your own custom blocks too.

You can then define where these appear – first sidebar, second sidebar, footer, navigation menu, etc, by selecting their position from the blocks menu. You can even do this on a theme by theme basis – on one theme you may want the search form to go in a sidebar for example, in another theme you may want it to go at the top or bottom of the page.

Unlike the widgets system in WordPress though, everything is a block in Drupal! Even the main page content so for some reason if you wanted to make your footer text display in the centre of the page and your main content display in your sidebar – you’re just a couple of clicks away from that!

Menus
Menus probably need the least explaining of all – it allows you to create menus which people can navigate around the site with. It is worth noting though, that items don’t appear in the menu automatically – you have to request that a piece of content (usually a static page) is given a menu link when creating or editing that piece of content.

Of course, you can create as many different menus as you want, assign different content (or any other links you want to add!) to different menus, and have the menus display in different places around your layout using the blocks system.

Conclusion
I hope this has presented you with a quick introduction to the fundamental concepts of Drupal. It is far more customisable that most other popular content management systems and as such has a steeper learning curve, but far more flexibility once understood.

If you’re using Propel ORM, you may want to select a range of primary keys. According to the documentation, you should be able to do this using code similar to the following.

BookQuery::create()->filterById(array('min' => 1, 'max' => 100));

However, what you find you get is that will return books with the ID of 1 and 100, but nothing else.

That is because Propel does not support ranges on IDs. This has been noted on the Propel GitHub issue tracker and will be resolved at some point in the future, but until then you have two possibilities.

Firstly, if you’re only looking to specify one value in the range, you can pass a criteria constant to filter by that.

BookQuery::create()->filterById(30, \Criteria::GREATER_THAN)->find();

You can also use LESS_THAN in the same way. Or, if you need a range with both ends specified, you can resort to the where() method.

BookQuery::create()->where('id BETWEEN 1 AND 100')->find();

Though that method requires you to use the database column names, rather than the PHP names used in Propel (yours may be the same, but I often rename mine for legacy reasons).

We recently launched Village Chief, a Facebook game in which you take on the role of a local village chief with the aim of growing your community into a thriving settlement.

The project was designed from the ground up to be highly scalable – Facebook cames can go viral very quickly so you need a system which can scale up very quickly if your game suddenly becomes very popular, or you risk losing out on huge amounts of market capitalisation.

First off, it’s written in Ruby. Ruby is a cool scripting language that is similar to Python and it’s popular web framework Ruby on Rails has received a lot of praise being the framework that Twitter and 37signal’s suite (Basecamp, Highrise, etc) are written in. It’s a very forgiving language, even compared to PHP, so if you like your static typing consider Scala instead, but for rapid web development, Ruby is a gem.

Despite the popularity of the Rails framework, I was looking for something a little more lightweight, so Village Chief is built using Sinatra. The documentation is a little underdeveloped but is never the less sufficient to get buy and lets you get a web application up and running nice and fast.

Ruby also includes a great module system called Ruby Gems (spot the earlier pun now 😉 ), a system similar to PHP’s PECL. The game makes heavy use of these – for example, using Koala to interact with Facebook and Dalli to handle our caching.

For a data source, it made sense to use a NoSQL solution. I originally settled on Apache Cassandra. It doesn’t have the flexibility or functionally of Mongo but it terms of raw speed it’s hard to beat and scales onto multiple servers with eventual consistency beautifully.

When it came to deployment, I decided to go with Amazon AWS’s DynamoDB instead. I’ll discuss more about why this was later but this meant rewriting the database interaction. This was easy to do thanks to our database abstraction layer and allowed us to continue using Cassandra for our testing systems while rolling out the production environment on DynamoDB.

Some data was also rolled out using SQLite. This was used for data such as the product catalogue which doesn’t contain user data – just things you can buy. Keeping it in an SQLite database allows us get quick access while still being able to query against the records – and importantly, allows us to version control our product catalogue.

To keep the database load down, some of the sorting was moved into the web server layer instead. On top of this we built a caching system using Memcache to save a lot of the data in memory, thus making things much faster.

When it came to deployment, I decided that Amazon’s EC2 cloud. You can start up a new server in under a minute, which is fantastic for scalability. Thanks to Amazon’s Elastic IPs, you can maintain a set of public IPs and map them to any one of your EC2 servers.

The servers are based on the latest Ubuntu release and to make sure that they are delivering content at top speed, I choose to go with the nginx web server rather than Apache, which works in conjunction with Passenger to provide the platform.

One limitation of EC2 is that you either have to allocate EBS (Elastic Block Storage) which adds additional cost, or use the ephemeral storage which you lose every time you turn the box off. The solution? Put everything into an external database so that we can switch boxes on and off without a problem – hence the decision to use DynamoDB rather than running Cassandra on the servers.

Code is then deployed using Capistrano which goes onto each of the boxes and performs a structed deployment that you can easily roll back, pulling the code direct from our Git repository.

That is a whistle-stop tour of the technologies used in Village Chief. If you have any questions about any of them, feel free to post a comment.