Matthew Byrne: the blog » Postcode

Postcode Widget – Part 3

admin — Mon, 25 Aug 2008 10:59:38 +0000

You can see a prototype version of the widget by clicking here.

Template engine

I attempted this built as single piece of php but it quickly became obvious that this was not the right approach. Instead I adapted a simple template engine from my faithful O’Reilly book. This allowed me to separate the logic from the markup

function FillTemplate($inName, $inValues = array()){

	$theTemplateFile = $_SERVER['DOCUMENT_ROOT'].'/templates/'.$inName;
	if($theFile = fopen($theTemplateFile, 'r')){
		$theTemplate = fread($theFile, filesize($theTemplateFile));
		fclose($theFile);
	}
	$theKeys = array_keys($inValues);
	foreach($theKeys as $theKey){
		$theTemplate = str_replace("\{$theKey}",$inValues[$theKey],$theTemplate);
	}

	return $theTemplate;
}

Map Logic

Here’s the source for the Map Logic. As an attempt to make the script secure you can see I’ve used a UK Postcode Regex from Stuart Wade to validate the form input. And also mysql_real_escape_string() on any database calls.

Any security tips would be greatly appreciated

The Map Logic uses four separate templates to handle the interaction, and the error state.

Integrating script with WordPress

After developing this script I discovered that WordPress can’t run PHP in the body of a post without a plugin. Strange. So I had to put the prototype on a loose page.

Take a look at the trick I used to capture the output of a WordPress tag so I could incorporate it into Map Logic, and then my templates. In this example I captured the footer code, then bound it to a template tag.

Postcode widget – Part 2

admin — Sat, 16 Aug 2008 09:22:32 +0000

The Easypeasy Database

Today I’ve been testing the Easypeasy database for my widget project.

I began by installing the data to MySQL. Very easy to do as the downloadable zip comes with a file you can import directly into MyAdmin.

With the database installed I used two scripts to look at the data in more detail. Firstly, one to establish the initial database connecion – it’s an idea to keep this file separate so you only have to write it once. Then, a second script that builds a form and processes the results.

Once I started to plot my results it quickly became apparent that although Latitude and Longitude is returned for each entry, the numbers are all rounded up. This puts W10 and SE13 on the same spot, so there’s still a bit of work to do to figure out how to the x and y fields effect the results.

Here’s the code I wrote for the form:

<form action="<?php echo $_SERVER['PHP_SELF']?>" method="post">
Input Post Code:</br>&ltinput type="text" name="code" size="30">
<input type="submit" name="submit" value="submit">
</form>

<?php

//Connect to the database
include 'connect.php';

//If the form has been submitted then process the form
if (isset($_POST['code'])) {

//Grab the Postcode from the form
$postcode = $_POST['code'];

//Convert the Postcode to all uppercase
$postcode = strtoupper($postcode);

//Break the Postcode into two
list($outcode, $partTwo) = split(' ', $postcode);

//Pull out the relevant fields from our database
$query = "SELECT latitude,longitude FROM hwz_postcodes WHERE
outcode = '$outcode'";
$result = mysql_query($query) or die('Query failed: '.mysql_error());
$line = mysql_fetch_array($result, MYSQL_ASSOC);

//Print Results
print $postcode.' : ';
print $line['latitude'].','.$line['longitude'];

//We've finished with the database, so close the connection
mysql_close($conn);
}

?>

Postcode Widget – Part 1

admin — Thu, 31 Jul 2008 08:35:37 +0000

Background

After playing around with Google maps for a few days it became apparent that having a list of UK postcodes plus the corresponding latitude and longitude to each would come in very handy for a lot of people. If you had such a thing you could build loads of exciting applications, from route planning to food mile calculators.

The problem is that here in the UK the list doesn’t exist in the public domain. It’s available from the Post Office, but it’ll cost you, making it effectively useless for most small groups and enterprises.

What’s currently available from Easypeasy is the first half of the code. With this you can break the UK into about 3,000 separate parts, narrowing a location to within a few kilometres.

Project Brief

There appear to be two groups pushing the Postcode into the public domain, Free the Postcode and New Popular Edition Maps.

What I’d like to do is build a widget that people can put on their website that makes it easy for the general public to enter their Postcode, and help build the free database. Currently you are required to specifically visit either of the two website and with Free the Postcode know by heart your latitude and longitude.

Using the Google Map API combined with the first half of the postcode the widget would pull up a map of your local area, from here it’s easy to stick a pin where you live or work, and then after (an email?) authentication your postcode is added to the database.

References

Free the Postcode: www.freethepostcode.org

New Popular Edition Maps: www.npemap.org.uk

Postcode Schema: www.govtalk.gov.uk/gdsc/html/frames/PostCode.htm

Easypeasy: www.easypeasy.com/guides/article.php?article=64