The masthead on NAIS changes based on the local weather, temperature, and sunset and sunrise time. I added the daylight check at Doolies’s request. She didn’t understand why my weather doodle showed sunny at 5pm. This time of year, the sun sets at 4:29pm, and rises at 7:58am. I wish I was making this up.

First, I read in the XML file from the very helpful National Oceanic and Atmospheric Administration’s National Weather Service. They provide a number of great RSS feeds, of which I chose the hourly observations. I picked KRNT.xml, the feed for the Renton Municipal weather station, because it felt closest (knowing my geographic sense, I could be way off). Here’s the PHP code (remember, I can’t use file_get_contents() on a URL because of the PHP.ini security setting. I replaced it with the CURL call):

The code checks the weather once every thirty minutes, and saves the parsed result to a flat file. I use this file as a cache so I don’t have to reparse the XML file each time. There is higher-level page cache (which I plan to write more about) that also uses flat files to take the load off the MySQL server, which seems to be the bottleneck in serving pages.

I plan to generalize the above code a bit in the future so when I travel, I can replace Seattle with my destination (and its corresponding weather station). While this would be a trivial change, it’s not very high on my list.

After I load the XML file, I use the PHP xml parser to parse the document and find the weather description and temperature. I called xml_parse_into_struct() to perform the parsing. I still don’t quite understand how the structure is created. Through trial and error, I found the appropriate structure and array elements.

For the daylight check, I used the convenient PHP functions date_sunrise() and date_sunset(). These functions use the longitude and latitude and return sunset and sunrise times for the requested day.

And then I have the weather parsing code. As I add more weather doodles, I continue to tweak the code. It turns out the weather service uses many phrases to describe weather conditions. Some examples: “Thunderstorm in Vicinity Hail Haze,” “Showers in Vicinity Fog/Mist,” and “Heavy Sand Storm.” At first, I created a huge switch/case statement to capture all of the phrases. After a bit of thought, I decided to fall back on simpler phrase searches through an if/else statement. I set it up as a hierarchy to ensure the most desirable doodle is selected, e.g., if it’s “Light Drizzle Fog/Mist” it chooses the fog doodle—mostly because it’s less common. Similarly, if there’s a mention of snow or frozen rain, it chooses the snow doodle.

I will add a more robust temperature/season check once I have more relevant doodles. I’m hemming and hawing because I’m not satisfied with the following code. But I’ll include it for completeness.

My next step is to get doodling. It’s great to have all this code, but it’s wasted if my weather doodle is always the same. I plan to have a bunch of rain and cloudy doodles for the winter, and many sunny doodles for the summer. In Seattle, the word rain is much like the word snow is to Eskimos: you need many words (and doodles) to capture its essence.