Archive for the ‘Javascript’ Category

Google Maps API part 2: Retrieving Postcodes from your database

googlemaps part2

OK, this is a simple way to get your postcode/ address location returned and displayed via the Google Maps API on your own website. I’ll cover the ‘nearest store locator’ scenario in another post where you want places with a certain radius of an inputted postcode/ town returned.

First of all we need to retrieve our results which should already be stored with a geocoded result using the previous tutorial here. remember that in order for this to work you need an API key from google – again check the previous tutorial for more info on this.

We’re going to need to pass the geocoded values retrieved from the database into javascript and there are a few ways of doing this. This is really the hardest part and the only work you really need to do to display your result on a map as the Google maps API does the rest of the work for you. So we can either do this via something like an AJAX request whereby you build your returned data into an XML file and then use javascript to read that. Or you can write your php inline inside the javascript, which is messy for multiple results but in the singular it should be fine.

First lets start with the chunk of javascript on the page that will display our map etc… This method just calls up a map from the API and then zooms, centers and adds a marker to a specified co-ordinate. This singular display is useful if you want to, for instance, display the location of a result in a popup/ overlay.

// your API key here.



To see the map just add in a HTML element and set an onload event assigned to your body tag as thus

So now we just need to pass in our result from the database. Starting with passing it inline to javascript variable we can do the following, first connect and get your results from your database, very basically as below.

 LIMIT 1");

// assign the results to variables something like:
while ($row = @mysql_fetch_assoc($result)){
$lat = $row['lat'];
$lng = $row['lng'];
}
?>

Ok, so in javascript we can then put in our php values:


// declare variable to store co-ordinates - fetch these from your database

// var coords = new GLatLng(51, -1);
// or you can do this:
// var coords = new GLatLng(, );

So all together the php page will look something like this:

 LIMIT 1");

// assign the results to variables something like:
while ($row = @mysql_fetch_assoc($result)){
$lat = $row['lat'];
$lng = $row['lng'];
}
?>



For retrieving the results via an XML file instead I’ll cover that in part 3 as its much more applicable there.

Quick popup/overlay show and hide a layer with Javascript and CSS

css popup

Really quick and simple code in order to show or hide a layer on your webpage using Javascript.

Effectively what we do is define a layer in CSS and then write a couple of functions, one to set the visibility and position of the layer and the other to find the position on the page that it should appear. You can then add whatever you want inside the layer ready to be shown or hidden when a user clicks a link, or anyother way to activate the function.

Typically when we create a layer in CSS/ HTML it will appear inline in the page much like any other HTML element. We can position layers to be positioned either static, fixed, relative or absolute. This bit is important to know for our popup layer/ overlay and how to position it.

Static is where the layer appears in the page as it normally would where ever it’s placed in the code, much like an image in a page.

Fixed will allow a layer to stay in the same place in the browser window despite scrolling.

Relative is normally done with co-ordinates set from the layer’s original position on the page.

Absolute will mean the layer is positioned in relation to the parent element that it appears in or another given element in our case.

So first we declare our CSS.
We create a layer id using # and assign width, height, position, display and index parameters

	

Next we write our Javascript functions
We write a function to hide the layer, a function to show the layer and position it and a function to find the position of a given object to work out where to display the layer.

	

Finally we create our HTML
Here we create our layer and a couple of links, one to close the layer and one to open the layer, the function to open the layer needs the id of the layer to open and the object from which to position itself, in this case we use the link (this).

		
		
		Open

And here’s the final code:


	
	LUCKYLARRY.CO.UK - basic overlay, show/ hide a layer popup
	

	

	
	
		
		
		Open
	

Google Maps API part 1: Accurate Geocoding for UK Postcodes

googleMaps

Recently I had to build a system that would take an address, pass it to google and return latitude and longitude values. The result is then stored for later use and display on Google maps.

However, firstly I found that the default XML geocoding service provided by Google that allows you to do bulk geocoding on a data source and the geocoding provided by their maps API/ AJAX library (GClientGeocoder) had huge differences in results. Most postal codes passed to googles XML geocoding service were miles out or just not recognised. Yet when using the same postcode in the maps API when calculated on the fly the results were more or less spot on.

You can take a look at a tutorial for using Googles XML geocoder service, PHP and MySQL here. They suggest that this way is good if you don’t want to repeatedly geocode the same address again and again and if you want to do bulk geocoding.

Which would be nice, if it was actually accurate! But this still leaves me with having to do bulk uploads or geocoding and get accurate results to build, for instance, a store locator around the data.

The solution is simple, we can utilise the Google maps API to do the geocoding for us on the fly and store the result passed back using some simple AJAX to send the data to PHP/ MySQL. While I geocode my records at the time of their entry, in the example below, you could just as easily use this to create some sort of bulk update. Check out my tutorial here about using AJAX to pass form data to PHP if you’re new to this.

Firstly you will need to signup to get a couple of free API keys from google, you don’t require much to get them and they’ll work just fine for a localhost.

Maps API key: http://www.google.com/apis/maps/signup.html
AJAX Search API key: http://code.google.com/apis/ajaxsearch/signup.html

OK so now we create a HTML page, form.htm, this will call in the Javascript libraries and do the geocoding work.



We also build a function that creates an XML object in the DOM to store the data, which will then get passed to the PHP page. This works in exactly the same way as my tutorial here.


This chunk of code above is what utilises the google maps keys, to pass the data to google, geocode it and return the record and I've written this inside of a function that gets called on the form submission, which in turn then uses the previously declared XML creation function.

The final stage of this HTML page is of course the form which sends the data and a span tag that displays the results if successful.


Address Line 1:
Address Line 2:
Address Line 3:
Town:
Postcode:
 

Server-Response:

This then just leaves us the PHP page (post.php) that will then post the results, again nothing too disimilar to my previous tutorials on this. This is the bit where you would pass in the $_POST parameters and store them using MySQL etc... or save them to a text file.


And there we have it, accurate geocoding from google that can be used as a service when data is entered, or you could use this same method by passing in XML created from your database and iterating over this passing each result to the API and returning a value.

Now you can build a store locator or whatever that actually returns accurate results, also you can then use this to integrate your database better with the full Google maps API - showing maps, placing markers on maps etc..

Using Javascript/ AJAX to post HTML form data

javascript form ajax php

Why would you need to do this? Well for instance if you were using 3rd party AJAX APIs and you wanted to capture the data from them perhaps, or maybe you just have a complex form.

Or you could use this for form validation to return errors from the server without refreshing the browser, for example, if the data already exists in a database you could let the user know.

Either way its pretty simple. Basically we just use javascript to post the form object over http to a serverside page – e.g. PHP, JSP, ASP etc…

First of lets have a look at the javascript


And thats it, as for the HTML form, only thing to note is that the form action calls the sendData function:

* Address Line 1:
Address Line 2:
Address Line 3:
* Town:
* Postcode:
 
Server-Response:

Oh and of course the post.php page, in here you could add in your validation, check the database etc... what ever you ourput to the page (using print, echo etc...) can be then sent back to your form page and displayed without the user leaving your form page or refreshing the browser.


Creating XML from PHP/ MySQL for use with SPRY

So lets say for example you have a table in your database and you want to return some results, pretty easy with PHP/ MySQL and I dare say easy enough with other languages.

Now rather than return the results to the page and format them etc… you want to instead put them to an XML file – why? Well because creating a dataset in XML allows you to make use of various things both from a design point of view and from the prespective of user interaction. I’m of course talking about AJAX here (but also useful for XSLT etc…).

So assuming you are using PHP5, MySQL5 you can use the template below to do this. I’ve also used Adobe’s SPRY here, but jQuery or straight forward Javascript is easy enough. I’m going to assume you are also using SPRY – but there’s an example at the bottom using plain old javascript.

First stage: Create PHP page to build XML from database query

So this is my page: queryBuilder.php

It takes a parameter parsed via the URL GET method (q) and then loads the data based on this. Using this you can create a lot of different XML datasets served from just one page. Replace [text] with your own values.

createElement(‘[parent node]’);
$root = $doc->appendChild($root);
//create a document header to tell browsers what type of file this is
header(“Content-type: text/xml”);
//fetch data from your database table
$myList = mysql_query(“SELECT
ID,  Name
FROM mytable
ORDER BY Name ASC”);
// process one row at a time
while ($row = mysql_fetch_assoc($myTrades)) {

// add node for each row
$occ = $doc->createElement(‘[child node name]’);
$occ = $root->appendChild($occ);

// add a child node for each field
foreach ($row as $fieldname => $fieldvalue) {
$child = $doc->createElement($fieldname);
$child = $occ->appendChild($child);
$value = $doc->createTextNode($fieldvalue);
$value = $child->appendChild($value);
} // end foreach
} // end while

// get completed xml document
$xml_tradesList = $doc->saveXML();
//return xml page to the browser
echo $xml_tradesList;
} //end if q=

} //end if isset

//close db connection
mysql_close();
?>

Second stage: Create page to filter and display data.

So we can now fetch our dataset and use some javascript/AJAX call to get the XML. For simplicity I’m going to use SPRY, Adobes library, but you can just as easily use jQuery.

Creating a page called queryBuilder.htm first thing is to add in the framework libraries that you need available from Dreamweaver install or free from Adobes site (as linked):


Next we need to define our datasets – if you’re used to SPRY this should be easy enough for you.

So thats essentially it, SPRY calling in records from your database via a PHP page. Of course I’m assuming that you know how to display records in SPRY? No? Well here’s how to do it quickly for a select menu!

//declare a region for SPRY

//declare a region that will repeat all results in a loop

Easy huh?

Alternative to SPRY do it in Javascript

So with just Javascript a chunk of code such as below will do much the same thing as the SPRY code just you have to write more.

Make a file queryBuilder.js

//create variable to store the output of queryBuilder.php
var xmlhttp

// function to create an XML object
function GetXmlHttpObject()
{
if (window.XMLHttpRequest)
{
// code for IE7+, Firefox, Chrome, Opera, Safari
return new XMLHttpRequest();
}
if (window.ActiveXObject)
{
// code for IE6, IE5
return new ActiveXObject(“Microsoft.XMLHTTP”);
}
return null;
}

function showList(str)
{
xmlhttp=GetXmlHttpObject(); //function defined below
if (xmlhttp==null)
{
alert (“Your browser does not support AJAX!”);
return;
}
var url=”queryBuilder.php”;
url=url+”?q=”+str;
//this fetches the XML data in the DOM from the queryBuilder.php page
xmlhttp.onreadystatechange=stateChanged;
xmlhttp.open(“GET”,url,true);
xmlhttp.send(null);
}

function stateChanged()
{
//if XML has been loaded and is ready
if (xmlhttp.readyState==4)
{
// display the xml from queryBuilder.php to this HTML element
document.getElementById(“[Some HTML element]”).innerHTML=xmlhttp.responseText;
}
}

So now you can include this on your html page and call in the XML by calling the js function showList([data to load])

Using SPRY to fetch values from a URL

And then filter an XML file based on the values passed from the URL.

If you’re not aware, Adobe now has it’s own AJAX/Javascript library called SPRY for you to use and better yet they include this with Dreamweaver CS3. I assume that you already probably know of or use SPRY.

So lets assume you want to pass in a value via your URL to filter your data set, baring in mind that this will be a destructive filter. So for example your url is mysite.com/index.htm?myFilter=a

And for example your XML file is something like;

description description

For this to work you need to add in/ include these JavaScript files in your HTML file:



// These are needed to interface with the XML file

// This is whats used to get the values from the URL query string

And this is the code, if you’ve already used SPRY then you’ll understand some of this.

And now when you make your call to the data set as normal, it will still function, but when a value is passed into the myFilter variable in the URL, it will then filter the data and return only the matching results.

More can be found here from Adobe