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I had heard of Test Driven Development (TDD), an agile development technique, and I knew people I knew were using it. I started using it recently after I finally learned the philosophy behind TDD.

I had always understood it to be just a method of developing where you just make lots of unit tests. I've tried that and felt it was quite a lot of extra work, rather than just testing by hand as you go. I also thought it was mainly geared to Java-type development and not really web development. It turns out that it was boring and not beneficial because I was writing the tests after I wrote the code!

The secret to TDD is the whole "driven" part. You create the test before you write a single line of code. This makes you figure out what you want to do first, and forces you to structure the code in a way that makes testing easy. Basically, it forces each chunk of functionality to be in its own function, which makes the functionality more reusable.

Here's the basic process:

1. Write a test.
2. Run the test. Since you're writing a test before the functionality exists, it should definitely fail because you should be testing functionality that doesn't exist yet.
3. Next, create the simplest thing that makes the test pass. You can even cheat here if it's easier. The sooner you see a passing test, the better.
4. Once all the tests pass, you refactor your code to make it cleaner and more organized.
5. Commit to version control (optional).
6. Repeat.

You should also make sure you add a test whenever a bug creeps up, or whenever you realise there's some rule or assumption that needs to be made. Essentially, you should make a test any time you change the code. Often enough, you'll surprise yourself that things don't work the way you expect.

It turns out to be a lot of fun, and psychologically rewarding. By that I mean that you have short problems and successes. You see a red bar, solve the problem, and see a green bar a few minutes later. It makes you feel confident that you're building a system that works perfectly as expected.

The tools are definitely there for you:

• For PHP and CodeIgniter, I highly recommend SimpleTest and/or SimpleTester for CodeIgniter. SimpleTest comes with lots of different test types, so you can test MVC controllers by loading URLs, clicking links, and making sure everything is there as expected.
• For JavaScript and Ajax, there is JsUnit.
• You can also do browser-side testing with Selenium.
• And of course, Ruby on Rails is well known for its built-in testing features.

But even once you have the tools, you might look at your code and wonder where to start. I know I did. Without frequent unit testing, it's easy to end up with different functionality combined across multiple functions.

But you have to start somewhere. For the next piece of functionality you want to add, create a test for it first. This means you'll have to decide where that code will go. But how will you test the output?

It might occur to you that you could test the code easily if it were put into a single function in a library somewhere. This might involve creating a new class separate from everything you've done prior. You can always reorganize your existing code out of it's scrambled mess and into a set of easily testable, separated libraries and classes. You just need to start somewhere.

For more information do a Google search - there's tons written about it, and there are certainly libraries available for all the languages and frameworks you use.

Tags: agile

You may have heard that Google is hosting a number of Ajax APIs, including jQuery, prototype, script.aculo.us, MooTools and dojo.

Ajaxian actually has a good write-up of the benefits of this hosting. Long story short: Google's servers do caching and gzip compression as good or better than most of us know how to do, plus their web hosting is collocated and fast. On top of that, if we all were to get our sites to use the copy of jQuery on Google, our users will be more likely to have it cached before they ever visit our site.

To get started with jQuery 1.2.6, for example, you could just use this script tag:

<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.2.6/jquery.min.js"></script>

For other libraries and library loading techniques, check out the documentation.

All of this is really great, and I plan on using it on production sites in the future.. but can you spot the security hole this creates? How hard would it be for some disgruntled employee of Google to slip a few lines of evil JavaScript onto thousands (millions?) of web pages? Thankfully, Google's reputation is on the line as well, and I surely trust them to protect that!

Tags: links jquery ajax

I'm an English-speaking Canadian living in Germany. Quite often I go to a website like Google or Kayak and find myself looking at a German version of the site.

Okay, I do live in Germany, but why assume that everyone within Germany speaks German? What about visitors from other countries, or even people living here that would prefer to use another language?

What must be happening is these sites are taking my IP address, looking up the geographical location of that address, and choosing the official language for that country. This may work most of the time, but there is an even easier way to choose a language.

Most browsers send an Accept-Language header. For example, mine is set to:

en-ca,en;q=0.8,en-us;q=0.6,de-de;q=0.4,de;q=0.2

What this basically says is that I prefer (in decreasing order of preference) Canadian English, generic English, US English, German spoken in Germany, and lastly generic German. Any web site I visit is capable of looking at this list and deciding what language I would prefer.

Of course, no matter what assumptions you make about a visitor, give them a chance to change their language if needed. For example, if you use an Internet cafe in Berlin, you shouldn't be stuck viewing websites in German!

One really nice thing: I often see Google Ads and other geographically targeted ads in German, and this makes ignoring the ads much easier! :)

Update: I was inspired to throw together a quick Accept-Language parser in PHP:

$langs = array();

if (isset($_SERVER['HTTP_ACCEPT_LANGUAGE'])) {
    // break up string into pieces (languages and q factors)
    preg_match_all('/([a-z]{2}(-[a-z]{2})?)\s*(;\s*q\s*=\s*(1|0\.[0-9]+))?/', $_SERVER['HTTP_ACCEPT_LANGUAGE'], $lang_parse);

    if (count($lang_parse[1])) {
        // create a list like "en" => 0.8
        $langs = array_combine($lang_parse[1], $lang_parse[4]);
    	
        // set default to 1 for any without q factor
        foreach ($langs as $lang => $val) {
            if ($val === '') $langs[$lang] = 1;
        }

        // sort list based on value	
        arsort($langs, SORT_NUMERIC);
    }
}

// look through sorted list and use first one that matches our languages
foreach ($langs as $lang => $val) {
	if (strpos($lang, 'de') === 0) {
		// show German site
	} else if (strpos($lang, 'en') === 0) {
		// show English site
	} 
}

// show default site or prompt for language

This would produce the following structure for my Accept-Language string:

Array
(
    [en-ca] => 1
    [en] => 0.8
    [en-us] => 0.6
    [de-de] => 0.4
    [de] => 0.2
)

I succumbed to twitter. If anybody here twitters, feel free to follow me at @jesseskinner or leave your id in the comments.

Tags: about twitter

Three years ago today, I wrote my first post. I was just about to move to Berlin and was looking for a new job.

A lot has happened since then. I started freelancing a year later, and I couldn't have done it without this site. 100% of my clients come directly through my "hire me" page.

By the time this blog turns four, we should be living back in Canada, and I might set up a web development agency (in an office!)

That's enough about me! What're you guys up to these days?

Tags: about

Lately, I've been skipping using MySQL in situations where I just want to store a few variables, like configuration options, and don't necessarily want the hassle of setting up a database.

You can easily store data to a file using serialize and unserialize to turn a PHP object into a string, and then read and write the string in a file.

Here are a few functions that do just that:

function get_data($filename) {
    // create file if it doesn't exist
    if (!file_exists($filename)) {
        touch($filename);
    }

    return unserialize(file_get_contents($filename));
}

function get_option($filename, $key) {
    $data = get_data($filename);
    return $data[$key];
}

function set_option($filename, $key, $value) {
    $data = get_data($filename);
    $data[$key] = $value;

    // write to disk
    $fp = fopen($filename, 'w');
    fwrite($fp, serialize($data));
    fclose($fp);
}

// probably should put somewhere off the web root
$config = '../config.dat';

set_option($config, 'width', 1024);
echo get_option($config, 'width'); // will echo 1024

So there you have it. Feel free to use or modify this code as much as you like. If anyone has an idea for rewriting it to be cleaner, please share in the comments.

Tags: php

Web scraping is a technique of web development where you load a web page and "scrape" the data off the page to be used elsewhere. It's not pretty, but sometimes scraping is the only way to access data or content from a web site that doesn't provide RSS or an open API.

I'm not going to discuss the legal aspects of scraping, as it may be considered copyright infringement in some situations. However, there are also perfectly legal reasons to need to scrape, like if you have permission.

To make things really easy, we're going to let the power of regular expressions do all the work for us. If you're not familiar with regular expressions, you may want to google for a tutorial. Here is the documentation for PHP regular expression syntax.

First, we start off by loading the HTML using file_get_contents. Next, we use preg_match_all with a regular expression to turn the data on the page into a PHP array.

This example will demonstrate scraping this web site's blog page to extract the most recent blog posts. This is just for demo purposes - of course, the RSS feed is much better suited for this.

// get the HTML
$html = file_get_contents("http://www.thefutureoftheweb.com/blog/");

Here is what the HTML looks like for the blog posts:

<ul>
    <li>
        <h1><a href="[link]">[title]</a></h1>
        <span>[date]</span>
        <div>
            [content]
        </div>
    </li>
</ul>

So we will use a regular expression that looks for all the li elements and capture the content using parentheses at the appropriate places (link, title, date & content).

preg_match_all(
    '/<li>.*?<h1><a href="(.*?)">(.*?)<\/a><\/h1>.*?<span>(.*?)<\/span>.*?<div>(.*?)<\/div>.*?<\/li>/s',
    $html,
    $posts, // will contain the blog posts
    PREG_SET_ORDER // formats data into an array of posts
);

foreach ($posts as $post) {
    $link = $post[1]
    $title = $post[2];
    $date = $post[3];
    $content = $post[4];

    // do something with data
}

There's a lot going on inside that regular expression, but there are really only a few "tricks" that are used. Anytime I want to say "skip over whatever is between" I use .*?. And any time I want to say "match whatever is in here" I use (.*?). And lastly, the s at the end tells PHP to allow the dot . to match newlines. That's about all there is to it.

The regular expression will only match blog posts, because they are the only <li> elements that contain an <h1>, <span> and <div>.

Web scraping is highly unreliable - if the HTML structure were to change this code would break instantly. However, it's often quite easy to write this code, and usually produces a perfectly usable hack solution.

Tags: php web scrape

I've just added a new page where you can see a listing of all the articles I've written (this article is my 181st). This might be an easier way to see older articles than going page by page or month by month. Check it out: All Articles

Tags: about links

My second IBM developerWorks article is now online: Where and when to use Ajax in your applications.

It's not a very technical article, so you can read it even if you've never programmed before. I talk about the benefits of using Ajax, and point out some problem areas that need special attention so that Ajax doesn't end up ruining your web site. It's essentially a summary of my Unobtrusive Ajax book.

The article was fun to write and I hope you enjoy reading it!

Tags: links ajax javascript

The long-awaited new Code Igniter version just came out last week - check out the announcement, the download, the Change Log, and (if you're updating) the update instructions.

Tags: codeigniter ci code igniter 1.6.0