Converting UK PostCode To Longitude And Latitude With PHP

This common problem has stumped many programmers in the past, so I thought I would add in my little part. Whilst doing research for this I manged to find a site called www.streetmap.co.uk which has a nice little PostCode to geographical reference tool. Using a simple URL parameter I was able to give the site a PostCode and strip the longitude and latitude from the resulting HTML. Here is the function I came up with.

function postCode2Geog($code){


 $code = strtolower(str_replace(' ','',$code));


 $uri = "http://www.streetmap.co.uk/streetmap.dll?GridConvert?name=".$code."&type=Postcode";


 


 $ch = curl_init($uri);


 curl_setopt($ch, CURLOPT_HEADER, 0);


 curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);


 $output = curl_exec($ch);


 curl_close($ch);


 


 preg_match('#long \(wgs84\)\s*?\\s*?\\S{2,3}:\S{2}:\S{2} \( (.*?) \)#i',$output,$longMatch);


 preg_match('#lat \(wgs84\)\s*?\\s*?\\S{2,3}:\S{2}:\S{2} \( (.*?) \)#i',$output,$latMatch);


 $long = $longMatch[1];


 $lat = $latMatch[1];


 


 return array($lat,$long);


}


 


To use the function use the following, in this case I am looking at the BBC studio in  London.


 


$geog = postCode2Geog('W1A 1AA');


 


This produces the result of 51.518561 latitude and -0.143800 longitude, which seems to check out.


 


Initial results from using this method seem promising, but the Streetmap site seems not to have been updated since 2004.  I found this method after a few minutes searching, and I only needed to convert 20 or so postcodes into geographical coordinates.  An alternative is to use a method that I have talked about previously in the post find longitude and latitude of PostCode or ZipCode using Google Maps And PHP, but that requires you to have a valid, working Google maps API key.  This method is an alternative if you don't want to go down that route.