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About Me

Hi, I 'm Aditya, the guy behind this website and many other. This site acts as my web playground, where I share all about me, my work and my knowledge.

I have over 8 yrs hands on experience in PHP, Mysql, JavaScript, open sources CMS like Joomla, Wordpress etc. During these 8 years, I have worked on more than 200 projects and/or websites but could not spare time for my blog.

 

 

Posts Tagged ‘XML’

XML

About XML

Extensible Markup Language (XML) is described as both a markup language and a text based data storage format, depending on who you talk to. It is a subset of Standard Generalized Markup Language (SGML); it offers a text-based means to apply and describe a tree-based structure to information. XML serves as the basis for a number of languages/formats, such as Really Simple Syndication (RSS), Mozilla's XML User Interface Language (XUL), Macromedia's Maximum eXperience Markup Language (MXML), Microsoft's eXtensible Application Markup Language (XAML), and the open source Java XML UI Markup Language (XAMJ). As the many flavors of XML demonstrate, XML is a big deal. Everyone wants to get on the XML bandwagon.

Writing XML

XML's basic unit of data is the element. Elements are delimited by a start tag, such as , and an end tag, such as . If you have a start tag, you must have an end tag. If you fail to include an end tag for each start tag, your XML document is not well-formed, and parsers will not parse the document properly. Tags are usually named to reflect the type of content contained in the element. You would expect an element named book to contain a book title, such as Great American Novel (see Listing 1). The content between the tags, including the white spaces, is referred to as character data.

Listing 1. A sample XML document

 

<books>   
       
       <book>     
        <title>Great American Novel</title>       
		<characters>       
			<character>       <name>Cliff</name>       <desc>really great guy</desc>      </character>      <character>       <name>Lovely Woman</name>       <desc>matchless beauty</desc>      </character>      <character>       <name>Loyal Dog</name>       <desc>sleepy</desc>      </character>     </characters>     <plot>      Cliff meets Lovely Woman.  Loyal Dog sleeps, but wakes up to bark      at mailman.     </plot>     <success type="bestseller">4</success>     <success type="bookclubs">9</success>     </book>    </books> 

XML element and attribute names can consist of the upper case alphabet A-Z, the lower case alphabet a-z, digits 0-9, certain special and non-English characters, and three punctuation marks, the hyphen, the underscore, and the period. Other punctuation marks are not allowed in names.

XML is case sensitive. In this example, and describe two different elements. Either is an acceptable element name. It's probably not a good idea to use and to describe two different elements, as the possibility of clerical error seems high.

Each XML document contains one and only one root element. The root element is the only element in an XML document that does not have a parent. In the example above, the root element is . Most XML documents contain parent and child elements. The element has one child, . The element has four children, , , and . The element has three child elements, each of which is a element. Each element has two child elements, and .

In addition to the nesting of elements that create the parent-child relationships, XML elements can also have attributes. Attributes are name-value pairs attached to an element's start tag. Names are separated from values by an equal sign, =. Values are enclosed by single or double quotation marks. In Listing 1 above, the element possesses two attributes, "bestseller" and "bookclubs". There are different schools of thought among XML developers about the use of attributes. Most information contained in an attribute could be contained in a child element. Some developers insist that attribute information should be metadata, namely information about the data, and not the data itself. The data itself should be contained in elements. The choice of whether to use attributes or not really depends on the nature of the data and how data will be extracted from the XML.

Strengths of XML

One of XML's good qualities is its relative simplicity. You can write XML with basic text editors and word processors, no special tools or software required. The basic syntax for XML consists of nested elements, some of which have attributes and content. An element usually consists of two tags, a start tag and an end tag, each of which is bracketed by an open and a close < /tag >. XML is case sensitive and does not ignore white space. It looks a lot like HTML, which is familiar to a lot of people, but, unlike HTML, it allows you to name your tags to best describe your data. Some of XML's advantages are its self-documenting, human, and machine-readable format, its support for Unicode, which allows for internationalization in human language support, and its stringent syntax and parsing requirements. Unfortunately, UTF-8 is problematic in PHP5; this shortcoming is one of the forces driving the development of PHP6.

Weaknesses of XML

XML is wordy and redundant, with the attendant consequences of being large to store and a huge consumer of bandwidth. People are supposed to be able to read it, but it's hard to imagine a human trying to read an XML file with 7 million nodes. The most basic parser functionality doesn't support a wide array of data types; therefore, irregular or unusual data, which is common, is a primary source of difficulty.

Well-Formed XML An XML document is well-formed if it follows all of XML's syntax rules. If a document is not well-formed, it is not XML, in a technical sense. An HTML tag such as
is unacceptable in XML; the tag should be written
to be well-formed XML. A parser won't parse XML properly if it is not well-formed. Additionally, an XML document must have one and only one root element. Think of the one root element as being like an endless file cabinet. You have one file cabinet, but there are few limits as to what and how much you can fit into the file cabinet. There are endless drawers and folders into which you can stuff information.

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Last Updated on Sunday, 7 February 2010 05:15

 Shorthand for asynchronous JavaScript and XML, is a group of interrelated web development techniques used on the client-side to create interactive web applications. With Ajax, web applications can retrieve data from the server asynchronously in the background without interfering with the display and behavior of the existing page.

The use of Ajax techniques has led to an increase in interactive or dynamic interfaces on web pages. Data is usually retrieved using the XMLHttpRequest object. Despite the name, the use of JavaScript and XML is not actually required, nor do the requests need to be asynchronous.

AJAX is based on the following web standards:

  • JavaScript
  • XML
  • HTML
  • CSS

AJAX uses the XMLHttpRequest object

To get or send information from/to a database or a file on the server with traditional JavaScript, you will have to make an HTML form, and a user will have to click the "Submit" button to send/get the information, wait for the server to respond, then a new page will load with the results. Because the server returns a new page each time the user submits input, traditional web applications can run slowly and tend to be less user-friendly.

With AJAX, your JavaScript communicates directly with the server, through the JavaScript XMLHttpRequest object.

With the XMLHttpRequest object, a web page can make a request to, and get a response from a web server – without reloading the page. The user will stay on the same page, and he or she will not notice that scripts request pages, or send data to a server in the background.

To demonstrate the AJAX PHP connection we will create a very simple form with 2 input fields. In the first field you can type any text and we will send this text to our PHP script which will convert it to uppercase and sends it back to us

HTML code

<body>
	<form name="testForm">

	Input text: <input type="text" onkeyup="doWork();" 
	name="inputText" id="inputText" />

	Output text: <input type="text" name="outputText" 
	id="outputText" />

	</form>

</body>

1. First step

 // Get the HTTP Object 
 function getHTTPObject(){ 
 
	if (window.ActiveXObject) 

 		return new ActiveXObject("Microsoft.XMLHTTP"); 
  	else if (window.XMLHttpRequest) 
 
		return new XMLHttpRequest(); 
 
	else { 
 
		alert("Your browser does not support AJAX."); 
		return null; 
		} 
	}

2. Second Step

// Implement business logic 
 function doWork(){ 
 	 httpObject = getHTTPObject(); 
	 if (httpObject != null) {  
	 	httpObject.open("GET", "upperCase.php?
		inputText="+document.getElementById
		('inputText').value, true); 
		httpObject.send(null); 
		httpObject.onreadystatechange = setOutput; 
		} 
	 }

3. The last step on client side is to implement the setOutput() function which will change the value of our second field.

  • 0 = uninitialized
  • 1 = loading
  • 2 = loaded
  • 3 = interactive
  • 4 = complete
// Change the value of the outputText field 
 function setOutput(){ 
 	 if(httpObject.readyState == 4){ 
	 	document.getElementById('outputText').value 
		= httpObject.responseText; 
		} 
	 } 

 

Implementing the server side functionality is very simple compared to the client side. In the PHP code we just need to check the $_GET super-global array. Afterwards convert it to uppercase and echo the result. So the PHP code is this:

<?php if (isset($_GET['inputText']))
      	echo strtoupper($_GET['inputText']);
      ?>
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Last Updated on Saturday, 15 May 2010 11:54