Pop-up Image Widget using JavaScript, PHP and CSS

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If you’re a regular blog reader then it’s likely that you’ve encountered the Recent Visitors widget form (http://mybloglog.com). This widget displays the profile like name, picture and sites authored by members of Mybloglog who have recently visited your blog. In the Mybloglog widget, when you move the mouse cursor to the member’s picture, you’ll see a popup displaying a brief description of that member.

A glance at MyBlogLog widget

Pop-up Image Widget using JavaScript, PHP and CSS

The above image is of a MyBlogLog widget. As you can see in the right part of the widget, there is a list of the recent visitors to the blog from members of MyBlogLog. You may also have noticed that in the left part of the widget is a popup showing the details and an image of the visitor. This popup is displayed when the mouse is moved over the image on the widget.

Now, let’s look at the code which we got from MyBlogLog to display the above widget.

<script src="http://pub.mybloglog.com/comm3.php?mblID=2007121300465126&r=
widget&is=small&o=l&ro=5&cs=black&ww=220&wc=multiple">
</script>

In the above script element, the language and type attributes are not specified. Although they are optional attributes in HTML – you must specify a value in the type attribute to make the above syntax valid in an XHTML web page.

If you closely looked at the src attribute of the script element, you can see that the source page of the script is a .php file. You can use the JavaScript code with any file extension like .php , .asp, and so on , but whenever you use such a file in src attribute please note that the final output code of the file (after being parsed by server) should be a valid JavaScript code.

Creating pop-up image widget

This pop-up image widget is somewhat similar to MyBlogLog widget but it is a simplified version of that widget. This is a very simple widget with uses JavaScript, PHP and CSS. Here you’ll see four images in the widget and a pop-up image (corresponding to the chosen image) will be displayed when you move the mouse over it. After getting the core concept, you can extend the functionality to make this look fancier.

Pop-up Image Widget using JavaScript, PHP and CSS

Writing Code for Pop-up Image Widget

As I’ve already discussed, this widget is going to contain PHP code, JavaScript and a little bit of CSS as well. For this, you need to write the code in a PHP file with the .php extension.

First of all, declare the variables for storing the current mouse position and string variables for storing the string of the widget.

var widget_posx=0;
var widget_posy=0;
var widget_html_css='';

The widget_posx variable is to hold the x co-ordinate values of the mouse position on the screen, whereas, the widget_posy variable will store the y co-ordinate. The widget_html_css variable stores the HTML and CSS elements which will be used later in the code.

The (0,0) co-ordinate of the output devices like monitor is located at the top left position. So the mouse position 10,10 will be somewhere near the top left corner of monitor.

After declaring the variables, let’s define an event handler to track the mouse position on the web page.

document.onmousemove=captureMouse;

As you can see above, we’ve called a function captureMouse() When the mouse is moved anywhere on the document (web page), the event handler which is the function captureMouse() is called on the onmousemove event. The Document object represents the entire HTML document and can be used to access and capture the events of all elements on a page.

Each time a user moves the mouse one pixel, a mousemove event occurs. It engages system resources to process all mousemove events, hence, use this event carefully!

Now, let’s look at the code of the captureMouse() function.

function captureMouse(event)
{
if (!event){var event = window.event;}
if (event.pageX || event.pageY)
{
widget_posx = event.pageX;
widget_posy = event.pageY;
}
else if (event.clientX || event.clientY)
{
widget_posx = event.clientX;
widget_posy = event.clientY;
}

}

As you can see in the above function, the event variable is passed as a function parameter. This event variable is the JavaScript’s Event object. The Event object keeps track of various events that occur on the page, such as the user moving the mouse or clicking on the link, and allows you to react to them by writing code which is relevant to the event.

if (!event){var event = window.event;}

In the above code, the first line of the event handler ensures that if the browser doesn’t pass the event information to the above function, then we would obtain it from any explicit event registration of the window object.

We can track different activity in the document by the event object with the help of its various defined properties. For example, if eventObj is the event object and we’ve to track whether the ctrl key is pressed (or not) – we can use the following code in JavaScript: eventObj.ctrlKey

If we’ve assigned the x, y-position of mouse in the page using the pageX and pageY properties, we can also get the same mouse position of the mouse cursor using clientX and clientY property. Most browsers provide both pageX/pageY and clientX/clientY. Internet Explorer is the only current browser that provides clientX/clientY, but not pageX/pageY.

To provide cross-browser support, we’ve used both pageX/pageY and clientX/clientY to get the mouse co-ordinates in the document, and assigned them to the widget_posx and widget_posy variables accordingly.

Now, let’s look at widget_html_css variable, where we’re going to store the string which is going to be displayed in the widget.

widget_html_css+='<style type="text/css">';
widget_html_css+='.widgetImageCss';
widget_html_css+='{ margin:2px;border:1px solid
#CCCCCC;cursor:pointer}';
widget_html_css+='</style>';

As you can see in the string of the above variable, we’ve added the style for the HTML element with the class name widgetImageCss within the style element. When applied, this class in the HTML adds a 2 pixel margins ‘brown color border’ to the element. Furthermore, the mouse cursor will be converted into pointer (a hand) which is defined with the cursor attribute in CSS.

widget_html_css+='<div id="widget_popup"
style="position:absolute;z-index:10; display:none"
>&nbsp;</div>';

Using the above code, we’re adding a division element with id widget_popup to the DOM. We’ve also added style to this element using inline styling. The position attribute of this element is set to absolute so that this element can move freely without disturbing the layout of the document. The z-index property is used for stacking the order of the element and in the above element it is set 10 so that this element will be displayed above all the other elements of the document. Finally, the display property is set to none for hiding the element at first. Afterwards, this element will be displayed with the pop-up image using JavaScript in the document.

Elements can have negative stack orders i.e. you can set the z-index to -1 for an element. This will display it underneath the other elements on the page. Z-index only works on elements that have been positioned using CSS (such as position:absolute).

Now, the PHP part of the codes comes in. We’ve used PHP to add the images to the widget_html_css string variables of JavaScript.

We’ve used PHP in this part rather than using JavaScript for making this application flexible. JavaScript is a client side scripting language and can’t access the database or do any kind of server activity. Using PHP, you can extract and display the images from the database which might be the integral part of your desired widget.

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