[Article] Simple Remoting - Weather

[bpat1434]

As has been pointed out by a few emails and posts on the board, I am going to ammend my previous article with these posts.

I originally had used regular HTML with Regular Expressions to extrapolate information from a website. This was just to give the user a general step into RegEx and getting used to getting information to a string ([man]file_get_contents[/man]) and manipulating that string to get information.

There are much easier ways to get the weather information, and that's what this post will discuss. Below is a link to the National Oceanic and Atmospheric Association (NOAA pronounced No-ah) page where any State in the U.S.A. can find weather information.
NOAA Current Observation Feeds

They come in two forms: RSS and XML. I'll quickly go over both PHP 4 and PHP 5 versions (since PHP 5 now has SimpleXML in its core).

I will focus mainly on the XML feed, but the RSS feed would take the same general form.

PHP 4 Version
PHP 5 Version

[bpat1434]

With PHP 4, we have to use the old fashioned way of [man]file_get_contents/man and RegEx. Unless you have the PECL DOMXML installed on PHP4, this is the easy way to do it:

1. Get the feed into a string:

   <?php
   $weather = file_get_contents("http://www.weather.gov/data/current_obs/KBWI.xml");

2. Set up some RegEx patterns:

   $location = "@<location>([a-zA-Z0-9\,\-\_\s]*)</location>@";
   $farenheit = "@<temp_f>([0-9]*)</temp_f>@";
   $celcius = "@<temp_c>([0-9]*)</temp_c>@";
   $condition = "@<weather>([a-zA-Z\s]*)</weather>@";
   $obsvd = "@<observation_time_rfc822>([a-zA-Z0-9\,\:\-\s]*)</observation_time_rfc822>@";

3. Run them through preg_match_all()

   preg_match($location, $weather, $matches);
   $info['loc'] = $matches[1];
   preg_match($farenheit, $weather, $matches);
   $info['deg_f'] = $matches[1];
   preg_match($celcius, $weather, $matches);
   $info['deg_c'] = $matches[1];
   preg_match($condition, $weather, $matches);
   $info['condition'] = $matches[1];
   preg_match($obsvd, $weather, $matches);
   $info['observed'] = $matches[1];

4. Display our results:

   echo 'Temp: '.$info['deg_f'].' &deg;F ('.$info['deg_c'].' &deg;C)<br>
   Observed from '.$info['loc'].' at '.$info['observed'];
   ?>

So the entire thing would be:

<?php
## GET WEATHER INFO TO STRING
$weather = file_get_contents("http://www.weather.gov/data/current_obs/KBWI.xml");

## SET UP PATTERNS
$location = "@<location>([a-zA-Z0-9\,\-\_\s]*)</location>@";
$farenheit = "@<temp_f>([0-9]*)</temp_f>@";
$celcius = "@<temp_c>([0-9]*)</temp_c>@";
$condition = "@<weather>([a-zA-Z\s]*)</weather>@";
$obsvd = "@<observation_time_rfc822>([a-zA-Z0-9\,\:\-\s]*)</observation_time_rfc822>@";

## MATCH PATTERNS, GET INFORMATION
preg_match($location, $weather, $matches);
$info['loc'] = $matches[1];
preg_match($farenheit, $weather, $matches);
$info['deg_f'] = $matches[1];
preg_match($celcius, $weather, $matches);
$info['deg_c'] = $matches[1];
preg_match($condition, $weather, $matches);
$info['condition'] = $matches[1];
preg_match($obsvd, $weather, $matches);
$info['observed'] = $matches[1];

## DISPLAY INFORMATION
echo 'Temp: '.$info['deg_f'].' &deg;F ('.$info['deg_c'].' &deg;C)<br>
Observed from '.$info['loc'].' at '.$info['observed'];
?>

Giving us the following output:

Temp: 51 °F (11 °C)
Observed from Baltimore-Washington International Airport, MD at Mon, 30 Jan 2006 21:54:00 -0500 EST

[bpat1434]

Using the default SimpleXML class (released with PHP 5 only) we can simplify our PHP4 script to be essentially 2 lines:

<?php

## Instantiate the class, and read the XML document
$xml = simplexml_load_file("http://www.weather.gov/data/current_obs/KBWI.xml");

echo 'Temp: '.$xml->temp_f.' &deg;F ('.$xml->temp_c.' &deg;C)<br>
Observed from '.$xml->location.' at '.$xml->observation_time_rfc822;
?>

The lovely joys of PHP 5....

The SimpleXML class load the file, and then you just call the child nodes of the XML document that you want. So in this case, we'd get the following output:

Temp: 53 °F (12 °C)
Observed from Baltimore-Washington International Airport, MD at Mon, 30 Jan 2006 20:54:00 -0500 EST