code.extend()

Javascript Function call() and apply() explained

2013-11-11T16:46:00.001+05:30

First of all

every function in JavaScript is an object

which has some methods attached to it some are toString(), call(), and apply().
Read this article if you wonder what the difference is between a function and a method.

Every JavaScript object has a toString() method, for example, and we can use the toString() method on a function object to see its source code:

function foo()
{
    alert('x');
}

alert(foo.toString());

Because functions are objects they can have their own properties and methods, and we can treat them like data. "Functions as data" is important to remember for the next post, too, but for now we'll focus on two of a function's methods: apply(), and its counterpart: call().
Let's start with the following code:

var x = 10;

function f()
{
    alert(this.x);
}

f();

Here we have a global function by the name of f(). f() uses the this keyword to reference x, but notice we don't invoke the function through an instance of an object. So what object does this reference? this will reference the global object. The global object is where we defined the variable x. The above code does work and will show the value 10 in a dialog.
Both call() and apply() are methods we can use to assign the this pointer for the duration of a method invocation. As an example, here is how we could use the call() method:

var x = 10;
var o = { x: 15 };

function f()
{
    alert(this.x);
}

f();
f.call(o);

The first invocation of f() will display the value of 10, because this references the global object. The second invocation (via the call method) however, will display the value 15. 15 is the value of the x property inside object o. The call() method invokes the function and uses its first parameter as the this pointer inside the body of the function. In other words - we've told the runtime what object to reference as this while executing inside of function f().
Fiddling with the this pointer might sound funny, even perverse, to C++, Java, and C# programmers. What's next? Dogs sleeping with cats? Working nVidia drivers for Windows Vista? It's all part of the fun that is ECMAScript.
We can also pass arguments to the target function via call():

var x = 10;
var o = { x: 15 };
function f(message)
{
    alert(message);
    alert(this.x);
}

f("invoking f");
f.call(o, "invoking f via call");

The apply() method is identical to call(), except apply() requires an array as the second parameter. The array represents the arguments for the target method.



f("invoking f");
f.apply(o, ["invoking f through apply"]);

The apply() method is useful because we can build a function like createDelegate (from the last post) that doesn't care about the signature of the target method. The function can use apply() to pass all additional arguments to the target method via an array.

var o = { x: 15 };

function f1(message1)
{
    alert(message1 + this.x);
}

function f2(message1, message2)
{
    alert(message1 + (this.x * this.x) + message2);
}

function g(object, func, args)
{
    func.apply(object, args);
}

g(o, f1, ["the value of x = "]);
g(o, f2, ["the value of x squared = ", ". Wow!"]);

The problem here is the awkward syntax. We are forcing the caller to stuff arguments into an array just so we call apply(). Fortunately, there is a way to make the syntax easier, but we have to introduce one more topic: the arguments identifier.
In JavaScript, every function essentially has a variable length argument list. The means we can pass 5 parameters to a function even if the function only uses one argument. The following runs without error and displays "H":

function f(message)
{
    alert(message);
}

f("H", "e", "l", "l", "o");

If we did want to access the other arguments from inside f(), we can use the arguments keyword. arguments references an Arguments object, which has a length property and feels like an array.

function f(message)
{
    // message param is the same as arguments[0]    
   
    for(var i = 1; i < arguments.length; i++)
    {
        message += arguments[i];
    }
    
    alert(message); 
}

// this will say "Hello"
f("H", "e", "l", "l", "o");

Just so you know, arguments is technically not an array, even if it walks and talks like one. arguments has a length property but no split, push, or pop methods. What we can do with arguments inside our previous g() function is copy the incoming arguments after arguments[1] into an array object that we pass to apply.

var o = { x: 15 };

function f(message1, message2)
{
    alert(message1 + (this.x * this.x) + message2);
}

function g(object, func)
{           
    // arguments[0] == object
    // arguments[1] == func
    
    
    var args = []; // empty array
    // copy all other arguments we want to "pass through" 
    for(var i = 2; i < arguments.length; i++)
    {
        args.push(arguments[i]);
    }

    func.apply(object, args);
}

g(o, f, "The value of x squared = ", ". Wow!");

When we invoke g(), we can pass additional arguments as parameters instead of stuffing the arguments into an array.
At this point, we have the theoretical knowledge needed to understand call and apply, but perhaps you are already asking a question: what if I don't want to immediately invoke the target function f()? What if I just want to arrange all the players in this little drama so that I can invoke f() at some later point (as an event handler, for example), but still have this referencing the desired object.

Using `call` to invoke an anonymous function

In this purely constructed example, we create anonymous function and use call to invoke it on every object in an array. The main purpose of the anonymous function here is to add a print function to every object, which is able to print the right index of the object in the array. Passing the object as this value was not strictly necessary, but is done for explanatory purpose.

Hope this will help you understand, Feel free to ask anything

IOS Xcode Create a modal window

2013-07-02T18:08:00.000+05:30

Create a modal window for IOS application in Xcode

1. Create new view controller either programatically or using a nib file, design it the way you want your modal window to be.

2. Name it youtubeplayer (say).

3. Import its header file into the main view controller (obviously).

4. From the main view controller put the below code into any event. ( clicking of button, or table row selected etc.)

youtubeplayer *yt = [[youtubeplayer alloc] initWithNibName:@"youtubeplayer" bundle:[NSBundle mainBundle]]; yt.modalTransitionStyle = UIModalTransitionStyleCrossDissolve; yt.modalPresentationStyle = UIModalPresentationFormSheet; [self presentViewController:yt animated:YES completion:^{ NSLog(@"this is calleed"); }]; CGRect r = CGRectMake(self.view.bounds.size.width/2 - 350, self.view.bounds.size.height/2 - 200, 700, 400); r = [self.view convertRect:r toView:yt.view.superview.superview]; yt.view.superview.frame = r;

Also now you will need a button on the modal window opened to close it.
simply create a button or what ever element you are comfortable with and put in the following code in it.

- (IBAction)closeModal:(id)sender {

[self dismissModalViewControllerAnimated:YES];

}

that's it Now you are good to go.

If need any help You can ask in comments.

Happy Coding :)

Retrive the cover images of videos from YouTube

2013-07-01T18:52:00.001+05:30

Retrive the cover images of videos from YouTube

Each YouTube video has 4 generated images. They are predictably formatted as follows:

http://img.youtube.com/vi/<insert-youtube-video-id-here>/0.jpg
http://img.youtube.com/vi/<insert-youtube-video-id-here>/1.jpg
http://img.youtube.com/vi/<insert-youtube-video-id-here>/2.jpg
http://img.youtube.com/vi/<insert-youtube-video-id-here>/3.jpg

The first one in the list is a full size image and others are thumbnail images. The default thumbnail image (ie. one of 1.jpg, 2.jpg, 3.jpg) is:

http://img.youtube.com/vi/<insert-youtube-video-id-here>/default.jpg

For the high quality version of the thumbnail use a url similar to this:

http://img.youtube.com/vi/<insert-youtube-video-id-here>/hqdefault.jpg

There is also a medium quality version of the thumbnail, using a url similar to the HQ:

http://img.youtube.com/vi/<insert-youtube-video-id-here>/mqdefault.jpg

For the maximum resolution version of the thumbnail use a url similar to this:

(if it exists for certain videos youtube does not have a heigh resolution cover pic) .

http://img.youtube.com/vi/<insert-youtube-video-id-here>/maxresdefault.jpg

All of the above urls are available over https too. Just change http to https in any of the above urls.

Alternatively, you can use the YouTube API to get thumbnail images.

MySQL FULLTEXT Indexing and Searching

2013-03-01T02:08:00.000+05:30

MySQL has supported FULLTEXT indexes since version 3.23.23. VARCHAR and TEXT Columns that have been indexed with FULLTEXT can be used with special SQL statements that perform the full text search in MySQL.
To get started you need to define the FULLTEXT index on some columns. Like other indexes, FULLTEXT indexes can contain multiple columns. Here's how you might add a FULLTEXT index to some table columns:

ALTER TABLE news ADD FULLTEXT(headline, story);

Once you have a FULLTEXT index, you can search it using MATCH and AGAINST statements. For example:

SELECT headline, story FROM news
WHERE MATCH (headline,story) AGAINST ('Hurricane');

The result of this query is automatically sorted by relevancy.

MATCH

The MATCH function is used to specify the column names that identify your FULLTEXT collection. The column list inside the MATCHfunction must exactly match that of the FULLTEXT index definition, unless your search in boolean mode (see below).

AGAINST

The AGAINST function is where your full text search query goes. Besides the default natural language search mode, you can performboolean mode searches, and use query expansion.

Boolean Mode Searches

SELECT headline, story FROM news
WHERE MATCH (headline,story)
AGAINST ('+Hurricane -Katrina' IN BOOLEAN MODE);

The above statement would match news stories about hurricanes but not those that mention hurricane katrina.
See the MySQL documentation on Boolean Mode searches for more info.

Query Expansion

The Blind Query Expansion (or automatic relevance feedback) feature can be used to expand the results of the search. This often includes much more noise, and makes for a very fuzzy search.
In most cases you would use this operation if the users query returned just a few results, you try it again WITH QUERY EXPANSION and it will add words that are commonly found with the words in the query.

SELECT headline, story FROM news
WHERE MATCH (headline,story)
AGAINST ('Katrina' WITH QUERY EXPANSION);

The above query might return all news stories about hurricanes, not just ones containing Katrina.
A couple points about Full-Text searching in MySQL:

Searches are not case sensitive
Short words are ignored, the default minimum length is 4 characters. You can change the min and max word length with the variables ft_min_word_len and ft_max_word_len
Words called stopwords are ignored, you can specify your own stopwords, but default words include the, have, some - see default stopwords list.
You can disable stopwords by setting the variable ft_stopword_file to an empty string.
Full Text searching is only supported by the MyISAM storage engine.
If a word is present in more than 50% of the rows it will have a weight of zero. This has advantages on large datasets, but can make testing difficult on small ones.

Hierarchical queries in MySQL, Tree structures

2013-02-15T19:47:00.002+05:30

Hierarchical queries in MySQL, Managing tree like structures

I was wondering how to implement a hierarchical query in MySQL (using the ancestry chains version) for a single row, such that it picks up the parents (if any) and any children (if any).

The idea is, I want to be able to jump in at any point, provide an Id of some sort, and be able to draw out the entire hierarchy for that Id, both upwards and downwards.

We need to combine two queries here:

Original hierarchical query that returns all descendants of a given id (a descendancy chain)
A query that would return all ancestors of a given id (an ancestry chain)

An id can have only one parent, that’s why we can employ a linked list technique to build an ancestry chain, like shown in this article:

Sorting lists

Here’s the query to to this (no functions required):

SELECT  @r AS _id,
         (
         SELECT  @r := parent
         FROM    t_hierarchy
         WHERE   id = _id
         ) AS parent,
         @l := @l + 1 AS lvl
 FROM    (
         SELECT  @r := 1218,
                 @l := 0,
                 @cl := 0
         ) vars,
         t_hierarchy h
WHERE    @r <> 0

To combine two queries, we can employ a simple UNION ALL.

The only problem that is left to preserve the correct level, since the ancestry chain query conts levelbackwards, and the hierarchical query will count it starting from zero.

Let’s create a sample table and see what we get:

CREATE TABLE t_hierarchy (

id int(10) unsigned NOT NULL AUTO_INCREMENT,

parent int(10) unsigned NOT NULL,

PRIMARY KEY (id),

KEY ix_hierarchy_parent (parent, id)

) ENGINE=InnoDB DEFAULT CHARSET=utf8;

 

DELIMITER $$

CREATE PROCEDURE prc_fill_hierarchy (level INT, fill INT)

BEGIN

DECLARE _level INT;

DECLARE _fill INT;

INSERT

INTO    t_hierarchy (id, parent)

VALUES  (1, 0);

SET _fill = 0;

WHILE _fill < fill DO

INSERT

INTO    t_hierarchy (parent)

VALUES  (1);

SET _fill = _fill + 1;

END WHILE;

SET _fill = 1;

SET _level = 0;

WHILE _level < level DO

INSERT

INTO    t_hierarchy (parent)

SELECT  hn.id

FROM    t_hierarchy ho, t_hierarchy hn

WHERE   ho.parent = 1

AND hn.id > _fill;

SET _level = _level + 1;

SET _fill = _fill + POWER(fill, _level);

END WHILE;

END

$$

DELIMITER ;

 

DROP FUNCTION IF EXISTS hierarchy_connect_by_parent_eq_prior_id;

 

DELIMITER $$

 

CREATE FUNCTION hierarchy_connect_by_parent_eq_prior_id(value INT) RETURNS INT

NOT DETERMINISTIC

READS SQL DATA

BEGIN

DECLARE _id INT;

DECLARE _parent INT;

DECLARE _next INT;

DECLARE CONTINUE HANDLER FOR NOT FOUND SET @id = NULL;

 

SET _parent = @id;

SET _id = -1;

 

IF @id IS NULL THEN

RETURN NULL;

END IF;

 

LOOP

SELECT  MIN(id)

INTO    @id

FROM    t_hierarchy

WHERE   parent = _parent

AND id > _id;

IF @id IS NOT NULL OR _parent = @start_with THEN

SET @level = @level + 1;

RETURN @id;

END IF;

SET @level := @level - 1;

SELECT  id, parent

INTO    _id, _parent

FROM    t_hierarchy

WHERE   id = _parent;

END LOOP;      

END

$$

 

DELIMITER ;

 

START TRANSACTION;

CALL prc_fill_hierarchy(6, 5);

COMMIT;

Now, let’s try to UNION ALL the queries as is:

SELECT  CONCAT(REPEAT('    ', lvl  - 1), _id) AS treeitem, parent, lvl AS level
FROM    (
        SELECT  @r AS _id,
                (
                SELECT  @r := parent
                FROM    t_hierarchy
                WHERE   id = _id
                ) AS parent,
                @l := @l + 1 AS lvl
        FROM    (
                SELECT  @r := 1218,
                        @l := 0,
                        @cl := 0
                ) vars,
                t_hierarchy h
        WHERE   @r <> 0
        ORDER BY
                lvl DESC
        ) qi
UNION ALL
SELECT  CONCAT(REPEAT('    ', level  - 1), CAST(hi.id AS CHAR)), parent, level
FROM    (
        SELECT  hierarchy_connect_by_parent_eq_prior_id(id) AS id, @level AS level
        FROM    (
                SELECT  @start_with := 1218,
                        @id := @start_with,
                        @level := 0
                ) vars, t_hierarchy
        WHERE   @id IS NOT NULL
        ) ho
JOIN    t_hierarchy hi
ON      hi.id = ho.id

treeitem	parent	level
1	0	6
2	1	5
7	2	4
38	7	3
165	38	2
1218	165	1
5473	1218	1
24796	5473	2
24797	5473	2
24798	5473	2
24799	5473	2
24800	5473	2
5474	1218	1
24801	5474	2
24802	5474	2
24803	5474	2
24804	5474	2
24805	5474	2
5475	1218	1
24806	5475	2
24807	5475	2
24808	5475	2
24809	5475	2
24810	5475	2
5476	1218	1
24811	5476	2
24812	5476	2
24813	5476	2
24814	5476	2
24815	5476	2
5477	1218	1
24816	5477	2
24817	5477	2
24818	5477	2
24819	5477	2
24820	5477	2
36 rows fetched in 0.0014s (0.1447s)

We see that the hierarchical order is mangled: the first resultset is upside down, the second one is starting from level = 1.

To fix it, we need to change the code that calculates level a little.

First, we need to reverse the ancestry part.

This can be easily done by sorting it on lvl DESC:

SELECT  CONCAT(REPEAT('    ', level  - 1), _id) AS treeitem, parent, level
FROM    (
        SELECT  @r AS _id,
                (
                SELECT  @r := parent
                FROM    t_hierarchy
                WHERE   id = _id
                ) AS parent,
                @l := @l + 1 AS level
        FROM    (
                SELECT  @r := 1218,
                        @l := 0,
                        @cl := 0
                ) vars,
                t_hierarchy h
        WHERE   @r <> 0
        ORDER BY
                level DESC
        ) qi

treeitem	parent	level
1	0	6
2	1	5
7	2	4
38	7	3
165	38	2
1218	165	1
6 rows fetched in 0.0003s (0.0684s)

We now have it in correct order but with wrong level values.

Since a level is essentially a rownum here, we can just calculate it as a rownum instead:

SELECT  CONCAT(REPEAT('    ', level  - 1), id) AS treeitem, parent, level
FROM    (
        SELECT  _id AS id, parent,
                @cl := @cl + 1 AS level
        FROM    (
                SELECT  @r AS _id,
                        (
                        SELECT  @r := parent
                        FROM    t_hierarchy
                        WHERE   id = _id
                        ) AS parent,
                        @l := @l + 1 AS level
                FROM    (
                        SELECT  @r := 1218,
                                @l := 0,
                                @cl := 0
                        ) vars,
                        t_hierarchy h
                WHERE   @r <> 0
                ORDER BY
                        level DESC
                ) qi
        ) qo

treeitem	parent	level
1	0	1
2	1	2
7	2	3
38	7	4
165	38	5
1218	165	6
6 rows fetched in 0.0003s (0.0712s)

We disregard the previously selected level at all, leaving it only inside the inline view qi for ordering purposes.

Now, we need to merge the descendancy tree query, but with levels starting from 6, not from 1.

Since this query will come after the ancestry one, we can use accumulated value of @cl (which we used to calculate level in the previous query) as a seed.

To do that, we can take the level returned by the descendancy tree query, and just add @cl to it.

The only problem it to determine when we should increment @cl and when we should add it to level.

We will just use a boolean field which will help us to tell the sets apart.

Here’s the query to do it:

SELECT  CONCAT(REPEAT('    ', level - 1), CAST(id AS CHAR)),
        parent,
        level
FROM    (
        SELECT  id, parent, IF(ancestry, @cl := @cl + 1, level + @cl) AS level
        FROM    (
                SELECT  TRUE AS ancestry, _id AS id, parent, level
                FROM    (
                        SELECT  @r AS _id,
                                (
                                SELECT  @r := parent
                                FROM    t_hierarchy
                                WHERE   id = _id
                                ) AS parent,
                                @l := @l + 1 AS level
                        FROM    (
                                SELECT  @r := 1218,
                                        @l := 0,
                                        @cl := 0
                                ) vars,
                                t_hierarchy h
                        WHERE   @r <> 0
                        ORDER BY
                                level DESC
                        ) qi
                UNION ALL
                SELECT  FALSE, hi.id, parent, level
                FROM    (
                        SELECT  hierarchy_connect_by_parent_eq_prior_id(id) AS id, @level AS level
                        FROM    (
                                SELECT  @start_with := 1218,
                                        @id := @start_with,
                                        @level := 0
                                ) vars, t_hierarchy
                        WHERE   @id IS NOT NULL
                        ) ho
                JOIN    t_hierarchy hi
                ON      hi.id = ho.id
                ) q
        ) q2

CONCAT(REPEAT(‘ ‘, level – 1), CAST(id AS CHAR))	parent	level
1	0	1
2	1	2
7	2	3
38	7	4
165	38	5
1218	165	6
5473	1218	7
24796	5473	8
24797	5473	8
24798	5473	8
24799	5473	8
24800	5473	8
5474	1218	7
24801	5474	8
24802	5474	8
24803	5474	8
24804	5474	8
24805	5474	8
5475	1218	7
24806	5475	8
24807	5475	8
24808	5475	8
24809	5475	8
24810	5475	8
5476	1218	7
24811	5476	8
24812	5476	8
24813	5476	8
24814	5476	8
24815	5476	8
5477	1218	7
24816	5477	8
24817	5477	8
24818	5477	8
24819	5477	8
24820	5477	8
36 rows fetched in 0.0016s (0.1514s)

One more thing: use this if extremely necessary, and for small trees,, some times it crashes the Mysql server,

im still working on some more efficient solution.

Till Happy coding :)

Change the Url Arguments without Reloading the page

2013-01-22T19:11:00.003+05:30

Change the Url Arguments without Reloading the page

It was always a messy thing to deal with urls for different pages or resources on a website And the only method we got was location.hash AJAX applications to get back button and bookmarking support, and libraries like jQuery BBQ from Ben Alman made dealing with it cross browser a cinch. Now, with HTML5 coming of age, there is a new feature that aims to replace the use of location.hash with a better solution: pushState. Over on the Spoiled Milk blog, Jamie Appleseed describes the API as “a way to change the URL displayed in the browser through JavaScript without reloading the page.” It works on the history object like this:

window.history.pushState(data, "Title", "/new-url");

The last argument is the new URL. For security reasons you can only change the path of the URL, not the domain itself. The second argument is a description of the new state. And the first argument is some data that you might want to store along with the state.

In order to support the back and forward buttons you must be notified when they are clicked. You can do that using the window.onpopstateevent. This event gives you access to the state data that you passed topushState earlier. Of course, you can manually go back and forward with the standard history functions.

Currently, pushState has support from the latest versions of Safari and Chrome, and Firefox 4 will be supporting it as well. It is worth noting that Flickr is already using the API in their new layout. I think that this is really the correct way to be dealing with history management in JavaScript applications since it changes the real URL instead of just the hash. I’m very excited to see libraries like jQuery BBQ start to support this feature with fallback to the old hash trick.

If you’d like to read a more in depth overview of these new features, you should check out the aforementioned blog post by Jamie Appleseed. If reading specs is your thing, you can check out the relevant document

Social Media Sharing Links

2013-01-10T19:27:00.003+05:30

Creating custom social sharing widgets for your website

Ever bother to make a sharing widget, here is the required info, u need to know to make a global sharing platform. what you need to do is to simply create a link ( < a href="given url here >social media</a>" ) Set its URL to one of the provided below.

1. Twitter.

URL : https://twitter.com/intent/tweet?
ARGS :

text = Hello this is a message length must not exceed 50 chars

related = pulsepad

url = the intended url.

2. Facebook.

for open type posting

http://www.facebook.com/sharer.php?u=http%3A%2F%2Fpinkink.brightpinkstudio.com&t=Hellothere

if u have an application then be precise and use this

https://www.facebook.com/dialog/feed?
app_id=458358780877780&
link=https://developers.facebook.com/docs/reference/dialogs/&
picture=http://fbrell.com/f8.jpg&
name=Facebook%20Dialogs&
caption=Reference%20Documentation&
description=Using%20Dialogs%20to%20interact%20with%20users.&
redirect_uri=https://mighty-lowlands-6381.herokuapp.com/

3. Google +

https://plus.google.com/share?url=http://jack.artoir.com

4. Pintrest

http://pinterest.com/pin/create/button/?url=http%3A%2F%2Fbrightpinkstudio.com%2Fpinkink%2Fresources%2Fsocial-bookmarking-widgets%2F&
media=http%3A%2F%2Fwww.onlywire.com%2Fimages%2FMainIllustrationz.jpg&
description=10%20Social%20bookmarking%20widgets%20for%20your%20website%20or%20blog%20-%20analyzed%20and%20compared.

5. Linkedin

http://www.linkedin.com/shareArticle?mini=true&
url=http%3A%2F%2Fbrightpinkstudio.com%2Fpinkink%2Fresources%2Fsocial-bookmarking-widgets%2F&
title=10%20Social%20Bookmarking%20Widgets%20Compared%20%7C%20Design%20by%20BrightPink%20Studio&
summary=10%20Social%20bookmarking%20widgets%20for%20your%20website%20or%20blog%20-%20analyzed%20and%20compared.
&source=

6. tumbler

http://www.tumblr.com/share/link?
url=http%3A%2F%2Fwww.tumblr.com%2Fexamples%2Fshare%2Fsharing-links-to-articles.html&
name=Sharing%20links%20to%20articles&
description=This%20example%20uses%20an%20advanced%20Tumblr%20Button%20in%20the%20article's%20footer%20to%20let%20Tumblr%20users%20easily%20share%20a%20beautifully%20formatted%20link%20to%20this%20article%20on%20their%20blogs.

Some Useful methods Keywords

2012-11-29T12:37:00.005+05:30

Some Useful methods Keywords

C#
php . PHP_EOL; //new line
WebRTC : http://www.html5rocks.com/en/tutorials/webrtc/basics/

STREAM UPDATES WITH SERVER-SENT EVENTS (HTML 5 NATIVE)

2012-11-29T12:14:00.004+05:30

STREAM UPDATES WITH SERVER-SENT EVENTS (HTML 5 NATIVE WEBSOCKET API)

SUPPORTED BROWSERS:

O

PERAIESAFARIFIREFOXCHROME

See Browser compatibility history

INTRODUCTION

I wouldn't be surprised if you've stumbled on this article wondering, "What the heck are Server-Sent Events (SSEs)?" Many people have never heard of them, and rightfully so. Over the years, the specification has seen significant changes, and the API has taken somewhat of a backseat to newer, sexier communication protocols such as the WebSocket API. The idea behind SSEs may be familiar: a web app "subscribes" to a stream of updates generated by a server and, whenever a new event occurs, a notification is sent to the client. But to really understand Server-Sent Events, we need to understand the limitations of its AJAX predecessors, which includes:

Polling is a traditional technique used by the vast majority of AJAX applications. The basic idea is that the application repeatedly polls a server for data. If you're familiar with the HTTP protocol, you know that fetching data revolves around a request/response format. The client makes a request and waits for the server to respond with data. If none is available, an empty response is returned. So what's the big deal with polling? Extra polling creates greater HTTP overhead.

Long polling (Hanging GET / COMET) is a slight variation on polling. In long polling, if the server does not have data available, the server holds the request open until new data is made available. Hence, this technique is often referred to as a "Hanging GET". When information becomes available, the server responds, closes the connection, and the process is repeated. The effect is that the server is constantly responding with new data as it becomes available. The shortcoming is that the implementation of such a procedure typically involves hacks such as appending script tags to an 'infinite' iframe. We can do better than hacks!

Server-Sent Events on the other hand, have been designed from the ground up to be efficient. When communicating using SSEs, a server can push data to your app whenever it wants, without the need to make an initial request. In other words, updates can be streamed from server to client as they happen. SSEs open a single unidirectional channel between server and client.

The main difference between Server-Sent Events and long-polling is that SSEs are handled directly by the browser and the user simply has to listen for messages.

SERVER-SENT EVENTS VS. WEBSOCKETS

Why would you choose Server-Sent Events over WebSockets? Good question.

One reason SSEs have been kept in the shadow is because later APIs like WebSockets provide a richer protocol to perform bi-directional, full-duplex communication. Having a two-way channel is more attractive for things like games, messaging apps, and for cases where you need near real-time updates in both directions. However, in some scenarios data doesn't need to be sent from the client. You simply need updates from some server action. A few examples would be friends' status updates, stock tickers, news feeds, or other automated data push mechanisms (e.g. updating a client-side Web SQL Database or IndexedDB object store). If you'll need to send data to a server,XMLHttpRequest is always a friend.

SSEs are sent over traditional HTTP. That means they do not require a special protocol or server implementation to get working. WebSockets on the other hand, require full-duplex connections and new Web Socket servers to handle the protocol. In addition, Server-Sent Events have a variety of features that WebSockets lack by design such as automatic reconnection, event IDs, and the ability to send arbitrary events.

JAVASCRIPT API

To subscribe to an event stream, create an EventSource object and pass it the URL of your stream:

if (!!window.EventSource) {
  var source = new EventSource('stream.php');
} else {
  // Result to xhr polling :(
}

Note: If the URL passed to the EventSource constructor is an absolute URL, its origin (scheme, domain, port) must match that of the calling page.

Next, set up a handler for the message event. You can optionally listen for open and error:

source.addEventListener('message', function(e) {
  console.log(e.data);
}, false);

source.addEventListener('open', function(e) {
  // Connection was opened.
}, false);

source.addEventListener('error', function(e) {
  if (e.readyState == EventSource.CLOSED) {
    // Connection was closed.
  }
}, false);

When updates are pushed from the server, the onmessage handler fires and new data is be available in its e.data property. The magical part is that whenever the connection is closed, the browser will automatically reconnect to the source after ~3 seconds. Your server implementation can even have control over this reconnection timeout. See Controlling the reconnection-timeout in the next section.

That's it. Your client is now ready to process events from stream.php.

EVENT STREAM FORMAT

Sending an event stream from the source is a matter of constructing a plaintext response, served with a text/event-stream Content-Type, that follows the SSE format. In its basic form, the response should contain a "data:" line, followed by your message, followed by two "\n" characters to end the stream:

data: My message\n\n

MULTILINE DATA

If your message is longer, you can break it up by using multiple "data:" lines. Two or more consecutive lines beginning with "data:" will be treated as a single piece of data, meaning only one message event will be fired. Each line should end in a single "\n" (except for the last, which should end with two). The result passed to your message handler is a single string concatenated by newline characters. For example:

data: first line\n
data: second line\n\n

will produce "first line\nsecond line" in e.data. One could then use e.data.split('\n').join('') to reconstruct the message sans "\n" characters.

SEND JSON DATA

Using multiple lines makes it easy to send JSON without breaking syntax:

data: {\n
data: "msg": "hello world",\n
data: "id": 12345\n
data: }\n\n

and possible client-side code to handle that stream:

source.addEventListener('message', function(e) {
  var data = JSON.parse(e.data);
  console.log(data.id, data.msg);
}, false);

ASSOCIATING AN ID WITH AN EVENT

You can send a unique id with an stream event by including a line starting with "id:":

id: 12345\n
data: GOOG\n
data: 556\n\n

Setting an ID lets the browser keep track of the last event fired so that if, the connection to the server is dropped, a special HTTP header (Last-Event-ID) is set with the new request. This lets the browser determine which event is appropriate to fire. The message event contains a e.lastEventId property.

CONTROLLING THE RECONNECTION-TIMEOUT

The browser attempts to reconnect to the source roughly 3 seconds after each connection is closed. You can change that timeout by including a line beginning with "retry:", followed by the number of milliseconds to wait before trying to reconnect.

The following example attempts a reconnect after 10 seconds:

retry: 10000\n
data: hello world\n\n

SPECIFYING AN EVENT NAME

A single event source can generate different types events by including an event name. If a line beginning with "event:" is present, followed by a unique name for the event, the event is associated with that name. On the client, an event listener can be setup to listen to that particular event.

For example, the following server output sends three types of events, a generic 'message' event, 'userlogon', and 'update' event:

data: {"msg": "First message"}\n\n
event: userlogon\n
data: {"username": "John123"}\n\n
event: update\n
data: {"username": "John123", "emotion": "happy"}\n\n

With event listeners setup on the client:

source.addEventListener('message', function(e) {
  var data = JSON.parse(e.data);
  console.log(data.msg);
}, false);

source.addEventListener('userlogon', function(e) {
  var data = JSON.parse(e.data);
  console.log('User login:' + data.username);
}, false);

source.addEventListener('update', function(e) {
  var data = JSON.parse(e.data);
  console.log(data.username + ' is now ' + data.emotion);
}, false);

SERVER EXAMPLES

A simple server implementation in PHP:

<?php
header('Content-Type: text/event-stream');
header('Cache-Control: no-cache'); // recommended to prevent caching of event data.

/**
 * Constructs the SSE data format and flushes that data to the client.
 *
 * @param string $id Timestamp/id of this connection.
 * @param string $msg Line of text that should be transmitted.
 */
function sendMsg($id, $msg) {
  echo "id: $id" . PHP_EOL;
  echo "data: $msg" . PHP_EOL;
  echo PHP_EOL;
  ob_flush();
  flush();
}

$serverTime = time();

sendMsg($serverTime, 'server time: ' . date("h:i:s", time()));

Download the code

Here's a similiar implementation using Node JS:

var http = require('http');
var sys = require('sys');
var fs = require('fs');

http.createServer(function(req, res) {
  //debugHeaders(req);

  if (req.headers.accept && req.headers.accept == 'text/event-stream') {
    if (req.url == '/events') {
      sendSSE(req, res);
    } else {
      res.writeHead(404);
      res.end();
    }
  } else {
    res.writeHead(200, {'Content-Type': 'text/html'});
    res.write(fs.readFileSync(__dirname + '/sse-node.html'));
    res.end();
  }
}).listen(8000);

function sendSSE(req, res) {
  res.writeHead(200, {
    'Content-Type': 'text/event-stream',
    'Cache-Control': 'no-cache',
    'Connection': 'keep-alive'
  });

  var id = (new Date()).toLocaleTimeString();

  // Sends a SSE every 5 seconds on a single connection.
  setInterval(function() {
    constructSSE(res, id, (new Date()).toLocaleTimeString());
  }, 5000);

  constructSSE(res, id, (new Date()).toLocaleTimeString());
}

function constructSSE(res, id, data) {
  res.write('id: ' + id + '\n');
  res.write("data: " + data + '\n\n');
}

function debugHeaders(req) {
  sys.puts('URL: ' + req.url);
  for (var key in req.headers) {
    sys.puts(key + ': ' + req.headers[key]);
  }
  sys.puts('\n\n');
}

Download the code

sse-node.html:

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8" />
</head>
<body>
  <script>
    var source = new EventSource('/events');
    source.onmessage = function(e) {
      document.body.innerHTML += e.data + '<br>';
    };
  </script>
</body>
</html>

CANCEL AN EVENT STREAM

Normally, the browser auto-reconnects to the event source when the connection is closed, but that behavior can be canceled from either the client or server.

To cancel a stream from the client, simply call:

source.close();

To cancel a stream from the server, respond with a non "text/event-stream" Content-Type or return an HTTP status other than 200 OK(e.g. 404 Not Found).

Both methods will prevent the browser from re-establishing the connection.

A WORD ON SECURITY

From the WHATWG's section on Cross-document messaging security:

Authors should check the origin attribute to ensure that messages are only accepted from domains that they expect to receive messages from. Otherwise, bugs in the author's message handling code could be exploited by hostile sites.

So, as an extra level of precaution, be sure to verify e.origin in your message handler matches your app's origin:

source.addEventListener('message', function(e) {
  if (e.origin != 'http://example.com') {
    alert('Origin was not http://example.com');
    return;
  }
  ...
}, false);

Another good idea is to check the integrity of the data you receive:

Furthermore, even after checking the origin attribute, authors should also check that the data in question is of the expected format....

DEMO

A demo app written in PHP is available on googlecodesamples.com along with its source.

REFERENCES

Convert a DataTable to JSON string

2012-11-28T13:37:00.003+05:30

Convert a DataTable to JSON string

This article demonstrate how to convert a DataTable in c# to a JSON string.

var dt = new DataTable("MyTable");
dt.Columns.Add("ID");
dt.Columns.Add("Name");
dt.Columns.Add("Active");

dt.LoadDataRow(new[] {"ID1", "John", "True"}, true);
dt.LoadDataRow(new[] {"ID2", "Bill", "False"}, true);

JsonConvert.SerializeObject(DatatableToDictionary(dt, "ID"));



public Dictionary<string, Dictionary<string, object>> DatatableToDictionary(DataTable dt, string id)
{
    var cols = dt.Columns.Cast<DataColumn>().Where(c => c.ColumnName != id);
    return dt.Rows.Cast<DataRow>()
             .ToDictionary(r => r[id].ToString(), 
                           r => cols.ToDictionary(c => c.ColumnName, c => r[c.ColumnName]));
}

The output string will be :

{
  "ID1": {
    "Name": "John",
    "Active": "True"
  },
  "ID2": {
    "Name": "Bill",
    "Active": "False"
  }
}

Create custom events in c#

2012-11-27T16:42:00.002+05:30

Create custom event in C# and handle them

Consider the following code.

public class FeedsManager

{

public event Status onStatusChange;

public delegate void Status(string StatusText, int StatusPercent);

public void someMethod(){

......

........

if (onStatusChange!= null) onStatusChange("Starting...", 10);

.......

........

if (onStatusChange!= null) onStatusChange("Starting...", 10);

.......

}

//other methods...

}

1. Declare the event delegate

public delegate void Status(string StatusText, int StatusPercent);

As in this case Status is the event type taking two arguments one of type string and other integer. you can provide a custom name to event and pass many arguments of different types.

2. Now create the event

public event Status onStatusChange;

Create an event of the type of delegate you have created , here the name of event is onStatusChange.

3. Raising the event

if (onStatusChange!= null) onStatusChange("Starting...", 10);

first we have to check is an event handler is set, if yes then call the handler function and pass the desired arguments.

Note: you can raise a event as many time you want, but in the context of same class.

Creating the handlers for event.

FeedsManager FM = new FeedsManager();

FM.onStatusChange += new FeedsManager.Status(FM_onStatusChange);

void FM_onStatusChange(string StatusText, int StatusPercent)

{

//do what ever you want

}

Or alternatively you can create a handler function as

FM.onStatusChange += (msg, per) => {

//do whatever you want

};

Hope it helps you some where

happy coding.... :D

COMET Streaming in Internet Explorer

2012-11-26T20:11:00.002+05:30

COMET Streaming in Internet Explorer

Comet or Reverse AJAX or Server Push or long Lived AJAX Request, This is a technique which can be used to maintain a continuous connection to a web server and receive data instantly without making a new AJAX request or reloading the page. This can be used in effective chatting applications or real time update of page data.

The request/response nature of HTTP works very well for traditional web pages, but to build dynamic AJAX applications, it’s often desirable for the server to be able to send data to the client on its own schedule. You could imagine, for instance, scenarios like an online game, or an event viewer, where the server may want to notify the client of something on an irregular schedule.

The COMET model allows a web application to push data to the browser without the browser explicitly requesting it—the Wikipedia page is fairly comprehensive, but my favorite reference is the “Scaling with COMET” chapter by Dylan Schiemann in Steve Souders’ second book on web performance, Even Faster Websites. While improved alternatives (like Server-Sent Events and Web Sockets) will likely eventually take over, workable COMET implementations can run in any browser built in the last few years.
One challenge with using XMLHTTPRequest is that browsers behave differently when it comes to streaming of content. A common complaint against XMLHTTPRequest in IE was that it doesn’t stream content. More specifically, the responseText property cannot be queried when readyState=3 (Receiving) and it only becomes available when readyState=4 (Loaded). This means that while your JavaScript will know when the transfer of the response body starts, you must wait for the response to complete before examining it. If your goal is to stream down a “never-ending” stream of data, you’ll find that IE’s XHR object never gets to the Loaded readyState and thus you cannot examine the “partial” response.
We had planned on fixing this for IE8 but unfortunately found that we couldn’t do so easily. IE’s “native” XMLHTTPRequest is simply a wrapper around the existing MSXML implementation, and the MSXML implementation performs this buffering internally. Since IE doesn’t install MSXML, we couldn’t simply change that implementation ourselves.

Update: IE10's newly enhanced CORS-capable XmlHttpRequest implementation can now stream responses as they are read from the server.
I put together a simple Streaming Test page where you can examine the behavior of your browser. The test uses AJAX to download a stream that contains ten small blocks of data, each sent 1 second apart. An event handler attached to the onreadystatechange event displays what data has been received. It’s interesting to see how different browsers behave when you click the “Try XMLHTTPRequest” button:

IE cannot show the responseText until readyState=Loaded

Chrome 4.1 doesn’t get to readyState=2 until the entire response is available

Opera 10.51 appears to fire the onreadystatechange function only once when first entering readyState=3 (Receiving)

Firefox 3.6 and Safari 4 fire onreadystatechange as each block is received, and make these blocks available in the responseText property

One point to keep in mind about streaming content in this way with XHR—even in the browsers where XHR behavior works as you might hope—is that the responseText property will grow and grow, increasing the amount of memory consumed by your page. In past betas, we’ve found degenerate pages which will exhaust the system’s virtual memory if left running overnight.
In Internet Explorer 8, we introduced the new XDomainRequest object—beyond support for making cross-origin requests, this object directly wraps URLMon and thus it doesn’t inherit the buffering behavior for MSXML. Naturally, the IE8 enginering team had test cases which confirmed that XDomainRequest objects properly support streaming, calling the onprogress event as the response blocks are received from the network.
Unfortunately, it turns out that our official test suite was based on streaming large responses back to the client. The problem is that, by-default, URLMon (the network wrapper below XDomainRequest) will not bubble up notifications of download progress in the first 2kb of the response. So, if you click “Try XDomainRequest” button on the test page, you will find that you don’t see the onprogress notifications until the entire response is returned.
A workaround for this problem is to send down a two kilobyte “prelude” at the top of the response stream—my test simply sends 2kb of spaces. After that initial block is received, the onprogress event is fired as each subsequent block is received from the network. Interestingly, you will also find that this “prelude” workaround resolves the Chrome 4.1 XHR behavior described in Point #2 above. When you send this prelude, Chrome’s XHR object will get to readyState=3 and begin reporting blocks as they are received.
Until next time,
-Eric
PS: Folks using Fiddler to debug with streaming content should be aware of two factors. First, Fiddler buffers most HTTP responses by default—you must disable Fiddler's buffering if you want content to be streamed to the browser as it normally is. Second, it’s important to understand that Fiddler’s Response Inspectors will not show an incomplete HTTP response. For streaming responses that never end, Fiddler will not show the partial body unless you use the newly introduced COMETPeek command on the context menu. The COMETPeek command will copy the current partial response body into the Response Inspectors for your viewing pleasure.

Update: IE10's newly enhanced CORS-capable XmlHttpRequest implementation can now stream responses as they are read from the server.

Request , Get , Post in c#

2012-11-24T14:10:00.004+05:30

Request , Get , Post in c#

Receiving the client side posted data on server side in c#

var request = Request["q"];         // $_REQUEST
var post = Request.Form["q"];       // $_POST
var get = Request.QueryString["q"]; // $_GET

SQL SERVER place unique contraint on multiple column

2012-05-08T13:13:00.001+05:30

Problem:

The problem is that we want to create two columns of a table combined unique.
Ex: consider the table below.

EmpID DeptID1     1
1     2
2     1
3     2
4     5
5     2
1     1 
1     2

Now we have to maintain the integrity of these two columns combined, as you can see that last two rows are exact duplicate of 1st and 2nd rows which must not exists where as 2nd and 3rd rows are permissible.

Solution :

If you have already created a table then first remove these duplicate rows. Then execute the following SQL query in the query editor window or SQL command prompt.

ALTER TABLE table ADD CONSTRAINT AnyConstraintName UNIQUE (EmpID,DeptID)

Or at time of creating table :

CREATE TABLE T1 (
    EmpID int not null,
    DeptID int not null,
    /* Other Columns */
    constraint PK_T1 PRIMARY KEY (EmpID,DeptID)
)

Hope this will help...

Get the request complete event of ASP.NET Update Panel

2012-05-07T15:57:00.005+05:30

Problem :

This problem is related to the use of jquery with ASP.NET Update panel, I encountered it when i was trying to make a event scheduler using the update panel.
The problem was that when i load the new data in update panel, or when i fire an post-back asynchronously the event handlers of jquery attached to the previous dom inside the update panel gets lost. and i need to attach the events to newly updated dom elements.

Solution :

I begin my thought process and a ♫♪Tding♥♥♥ idea came into my mind, that when ever an ajax request is completed a request complete event is fired. Thus i need to capture this event and reinitialize my jquery code at the request completion.

After reading a lot of documentations over Microsoft AJAX i discovered the code below.

Sys.WebForms.PageRequestManager.getInstance().add_endRequest( yourCallBackFunction );

And yes this line of code calls your function when ever any ajax request completes on the page. and of course this is the extension to Microsoft AJAX Framework.

Below is a complete demo of code.

Sys.WebForms.PageRequestManager.getInstance().add_endRequest(
function () {

$('#Calender li').each(function (index) {
var Prev = $(this);
$(this).find('p').click(function () {
Prev.find('p').css('background-color', '');
$(this).css('background-color', '#111');
});
})

});

simply you can test as: (or i must say cup cake steps)

1. put a scriptmanager on the page
2. place an update panel on your page
3. put some buttons inside update panel
4. copy the following code and paste somewhere inside your page

<script type="text/javascript">

Sys.WebForms.PageRequestManager.getInstance().add_endRequest(
function () {
alert('Request completed');
});

</script>

Thanks for reading hope this will help you some where..

COMET or Reverse Ajax

2012-04-16T16:51:00.002+05:30

This concept is the solution of problem that,

How to send data from a server to a client without a native HTTP request made by client.This can be implemented in Chatting Applications, Automatic updates of some data.

So what is this ?

Comet is a programming technique that enables web servers to send data to the client without having any need for the client to request it. It allows creation of event-driven web applications which are hosted in the browser.

Try reading from this . http://en.wikipedia.org/wiki/Comet_%28programming%29

From where do i got to know of this is http://stackoverflow.com/questions/3226688/web-chat-application-asp-net-jabber-ajax-wcf-comet-reverseajax-issues-faced

Here is finally wot i got and believe me its Awesome :)

1. create a new c# web application

2. Add a new page name it Services.aspx
3. in the code file i.e. Services.aspx.cs add the following code.

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

public partial class Service : System.Web.UI.Page
{
public static string Delimiter = "|";

protected void Page_Load(object sender, EventArgs e)
{
Response.Buffer = false;

while (true)
{
Response.Write(Delimiter + DateTime.Now.ToString("HH:mm:ss.FFF"));
Response.Flush();

// Suspend the thread for 1/2 a second
System.Threading.Thread.Sleep(500);
}

// Yes I know we'll never get here, it's just hard not to include it!
Response.End();
}
}

4. Good Now add a html page say home.html and add this code to it.

<html xmlns="http://www.w3.org/1999/xhtml" >

<head>

    <title>Comet AJAX Sample</title>

    <script language="javascript">

      function getData()

{

          loadXMLDoc("Service.aspx");

}

      var req = false;

      function createRequest()

{

        // branch for native XMLHttpRequest object

        if(window.XMLHttpRequest && !(window.ActiveXObject))

{

          try {

            req = new XMLHttpRequest();

          } catch(e) {

      req = false;

}

        // branch for IE/Windows ActiveX version

        } else if(window.ActiveXObject) {

          try {

            req = new ActiveXObject("Msxml2.XMLHTTP");

          } catch(e) {

            try {

          req = new ActiveXObject("Microsoft.XMLHTTP");

         } catch(e) {

          req = false;

}

}

}

}

      function loadXMLDoc(url) {

try

{

              if (req) {

                  req.abort();

                  req = false;

}

              createRequest();

              if (req) {

              req.onreadystatechange = processReqChange;

              req.open("GET", url, true);

              req.send("");

}

           else {

               alert('unable to create request');

}

}

       catch (e) {

           alert(e.message);

}

}

      function processReqChange() {

          if (req.readyState == 3) {

try

{

                  ProcessInput(req.responseText);

                  // At some (artibrary) length 

                  // recycle the connection

                  if (req.responseText.length > 3000) {

                      lastDelimiterPosition = -1;

                      getData();

}

}

              catch (e) {

                  alert(e.message);

}

}

}

      var lastDelimiterPosition = -1;

      function ProcessInput(input)

{

          // Make a copy of the input

          var text = input;

          // Search for the last instance of the delimiter

          var nextDelimiter = 

                text.indexOf('|', lastDelimiterPosition+1);

          if (nextDelimiter != -1) {

              // Pull out the latest message

              var timeStamp = text.substring(nextDelimiter+1);

              if (timeStamp.length > 0) {

                  lastDelimiterPosition = nextDelimiter;

                  ProcessTime(timeStamp);

}

}

}

      function ProcessTime(time)

{

          var out = document.getElementById('outputZone');

          out.innerHTML = time;

}

    </script>

</head>

<body onload="getData()">

    <b>Server Time:</b>&nbsp;&nbsp;<span id="outputZone"></span>

</body>

</html>

5. And yes you have done it Now run your html page.

You will see that the time is Continuously updating and yeah this is server time also check out that the browser is not sending any AJAX requests.

Adding a custom control Dynamically to a page in ASP.NET

2012-04-14T15:45:00.000+05:30

Adding a custom control Dynamically to a page in ASP.NET

1. Create a control .ascx file into your project Header.ascx (say).

2. Then add a refrence to your control

<%@ Reference Control="~/modules/controls/Header.ascx"%>

3. Then in C# use below code
(controls are listed in ASP namespace)

ASP.Header header_ctrl= (ASP.Header)LoadControl("~/Header.ascx");

Placeholder.Controls.Add(header_ctrl);

here Header is custom control and Placeholder is a panel.

Getting Started With PHP

2011-01-25T23:17:00.000+05:30

PHP - Stands for Hypertext PreProcessor

What is PHP ?
PHP is a server side scripting language, it is a widely used, general-purpose scripting language that was originally designed for web development to produce dynamic web pages. For this purpose, PHP code is embedded into the HTML source document and interpreted by a web server with a PHP processor module, which generates the web page document. As a general-purpose programming language, PHP code is processed by an interpreter application in command-line mode performing desired operating system operations and producing program output on its standard output channel. It may also function as a graphical application. PHP is available as a processor for most modern web servers and as a standalone interpreter on most operating systems and computing platforms.. It is An open source language So feel free to create your website.

How to begin with PHP ?
To Start doing Php all you need is a php server eg. Apache Or Wamp Server will do. in these tutorials im using the wamp server for testing. you can Download it from here .after installing start the wamp server then at the taskbar click on the icon of of wamp server >> localhost if the webpage of wamp sserver is displayed then it is ok to proceed. now you have to place all your php files in the www directory of wamp server. you can reach there by click wamp server in taskbar>> www directory and paste your php file there, then open the wamp server start page again this time you will find the name of your folder or php file on the page click it and select the file to run.

Programming Style:
The PHP interpreter only executes PHP code within its delimiters. Anything outside its delimiters is not processed by PHP (although non-PHP text is still subject to control structures described within PHP code). The most common delimiters are <?php to open and ?> to close PHP sections. <script language="php"> and </script> delimiters are also available, as are the shortened forms <? or <?= (which is used to echo back a string or variable) and ?> as well as ASP-style short forms <% or <%= and %>. While short delimiters are used, they make script files less portable as support for them can be disabled in the PHP configuration, and so they are discouraged. The purpose of all these delimiters is to separate PHP code from non-PHP code, including HTML.

The first form of delimiters, <?php and ?>, in XHTML and other XML documents, creates correctly formed XML 'processing instructions'.This means that the resulting mixture of PHP code and other markup in the server-side file is itself well-formed XML.

Variables are prefixed with a dollar symbol and a type does not need to be specified in advance. Unlike function and class names, variable names are case sensitive. Both double-quoted ("") and heredoc strings allow the ability to embed a variable's value into the string. PHP treats newlines as whitespace in the manner of a free-form language (except when inside string quotes), and statements are terminated by a semicolon. PHP has three types of comment syntax: /* */ marks block and inline comments; // as well as # are used for one-line comments. The echo statement is one of several facilities PHP provides to output text (e.g. to a web browser).

In terms of keywords and language syntax, PHP is similar to most high level languages that follow the C style syntax. if conditions, for and while loops, and function returns are similar in syntax to languages such as C, C++, Java and Perl.

Example :

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8" />
    <title>PHP Test</title>
  </head>
  <body>
  <?php
  echo 'Hello World';
  /* echo("Hello World"); works as well, although echo isn't a
  function, but a language construct. In some cases, such
  as when multiple parameters are passed to echo, parameters
  cannot be enclosed in parentheses. */
  ?>
  </body>
</html>

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