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Showing posts with label XML. Show all posts

Monday, 11 July 2011

AJAX :: RSS Reader

An RSS Reader is used to read RSS Feeds.

AJAX RSS Reader

The following example will demonstrate an RSS reader, where the RSS-feed is loaded into a webpage without reloading:

Example Explained - The HTML Page

When a user selects an RSS-feed in the dropdown list above, a function called "showResult()" is executed. The function is triggered by the "onchange" event:

<html>
<head>
<script type="text/javascript">
function showRSS(str)
{
if (str.length==0)
{
  document.getElementById("rssOutput").innerHTML="";
return;
}
if (window.XMLHttpRequest)
{// code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp=new XMLHttpRequest();
}
else
{// code for IE6, IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.onreadystatechange=function()
{
if (xmlhttp.readyState==4 && xmlhttp.status==200)
    {
    document.getElementById("rssOutput").innerHTML=xmlhttp.responseText;
    }
}
xmlhttp.open("GET","getrss.php?q="+str,true);
xmlhttp.send();
}
</script>
</head>
<body>

<form>
<select onchange="showRSS(this.value)">
<option value="">Select an RSS-feed:</option>
<option value="Google">Google News</option>
<option value="MSNBC">MSNBC News</option>
</select>
</form>
<br />
<div id="rssOutput">RSS-feed will be listed here...</div>
</body>
</html>

The showResult() function does the following:

Check if an RSS-feed is selected
Create an XMLHttpRequest object
Create the function to be executed when the server response is ready
Send the request off to a file on the server
Notice that a parameter (q) is added to the URL (with the content of the dropdown list)

The PHP File

The page on the server called by the JavaScript above is a PHP file called "getrss.php":

<?php
//get the q parameter from URL
$q=$_GET["q"];

//find out which feed was selected
if($q=="Google")
  {
  $xml=("http://news.google.com/news?ned=us&topic=h&output=rss");
  }
elseif($q=="MSNBC")
  {
  $xml=("http://rss.msnbc.msn.com/id/3032091/device/rss/rss.xml");
  }

$xmlDoc = new DOMDocument();
$xmlDoc->load($xml);

//get elements from "<channel>"
$channel=$xmlDoc->getElementsByTagName('channel')->item(0);
$channel_title = $channel->getElementsByTagName('title')
->item(0)->childNodes->item(0)->nodeValue;
$channel_link = $channel->getElementsByTagName('link')
->item(0)->childNodes->item(0)->nodeValue;
$channel_desc = $channel->getElementsByTagName('description')
->item(0)->childNodes->item(0)->nodeValue;

//output elements from "<channel>"
echo("<p><a href='" . $channel_link
  . "'>" . $channel_title . "</a>");
echo("<br />");
echo($channel_desc . "</p>");

//get and output "<item>" elements
$x=$xmlDoc->getElementsByTagName('item');
for ($i=0; $i<=2; $i++)
  {
  $item_title=$x->item($i)->getElementsByTagName('title')
  ->item(0)->childNodes->item(0)->nodeValue;
  $item_link=$x->item($i)->getElementsByTagName('link')
  ->item(0)->childNodes->item(0)->nodeValue;
  $item_desc=$x->item($i)->getElementsByTagName('description')
  ->item(0)->childNodes->item(0)->nodeValue;

  echo ("<p><a href='" . $item_link
  . "'>" . $item_title . "</a>");
  echo ("<br />");
  echo ($item_desc . "</p>");
  }
?>

When an RSS-feed is sent from the JavaScript, the following happens:

Check which feed was selected
Create a new XML DOM object
Load the RSS document in the xml variable
Extract and output elements from the channel element
Extract and output elements from the item element

AJAX :: Live Search

AJAX can be used to create more user-friendly and interactive searches.

AJAX Live Search

The following example will demonstrate a live search, where you get search results while you type.
Live search has many benefits compared to traditional searching:

Results are shown as you type
Results narrow as you continue typing
If results become too narrow, remove characters to see a broader result

Search for a W3Schools page in the input field below:
The results in the example above are found in an XML file (links.xml). To make this example small and simple, only eight results are available.

Example Explained - The HTML Page

When a user types a character in the input field above, the function "showResult()" is executed. The function is triggered by the "onkeyup" event:

<html>
<head>
<script type="text/javascript">
function showResult(str)
{
if (str.length==0)
{
  document.getElementById("livesearch").innerHTML="";
  document.getElementById("livesearch").style.border="0px";
return;
}
if (window.XMLHttpRequest)
{// code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp=new XMLHttpRequest();
}
else
{// code for IE6, IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.onreadystatechange=function()
{
if (xmlhttp.readyState==4 && xmlhttp.status==200)
    {
  document.getElementById("livesearch").innerHTML=xmlhttp.responseText;
    document.getElementById("livesearch").style.border="1px solid #A5ACB2";
    }
}
xmlhttp.open("GET","livesearch.php?q="+str,true);
xmlhttp.send();
}
</script>
</head>
<body>

<form>
<input type="text" size="30" onkeyup="showResult(this.value)" />
<div id="livesearch"></div>
</form>

</body>
</html>

Source code explanation:
If the input field is empty (str.length==0), the function clears the content of the livesearch placeholder and exits the function.
If the input field is not empty, the showResult() function executes the following:

Create an XMLHttpRequest object
Create the function to be executed when the server response is ready
Send the request off to a file on the server
Notice that a parameter (q) is added to the URL (with the content of the input field)

The PHP File

The page on the server called by the JavaScript above is a PHP file called "livesearch.php".
The source code in "livesearch.php" searches an XML file for titles matching the search string and returns the result:

<?php
$xmlDoc=new DOMDocument();
$xmlDoc->load("links.xml");

$x=$xmlDoc->getElementsByTagName('link');

//get the q parameter from URL
$q=$_GET["q"];

//lookup all links from the xml file if length of q>0
if (strlen($q)>0)
{
$hint="";
for($i=0; $i<($x->length); $i++)
  {
  $y=$x->item($i)->getElementsByTagName('title');
  $z=$x->item($i)->getElementsByTagName('url');
  if ($y->item(0)->nodeType==1)
    {
    //find a link matching the search text
    if (stristr($y->item(0)->childNodes->item(0)->nodeValue,$q))
      {
      if ($hint=="")
        {
        $hint="<a href='" .
        $z->item(0)->childNodes->item(0)->nodeValue .
        "' target='_blank'>" .
        $y->item(0)->childNodes->item(0)->nodeValue . "</a>";
        }
      else
        {
        $hint=$hint . "<br /><a href='" .
        $z->item(0)->childNodes->item(0)->nodeValue .
        "' target='_blank'>" .
        $y->item(0)->childNodes->item(0)->nodeValue . "</a>";
        }
      }
    }
  }
}

// Set output to "no suggestion" if no hint were found
// or to the correct values
if ($hint=="")
  {
  $response="no suggestion";
  }
else
  {
  $response=$hint;
  }

//output the response
echo $response;
?>

If there is any text sent from the JavaScript (strlen($q) > 0), the following happens:

Load an XML file into a new XML DOM object
Loop through all <title> elements to find matches from the text sent from the JavaScript
Sets the correct url and title in the "$response" variable. If more than one match is found, all matches are added to the variable
If no matches are found, the $response variable is set to "no suggestion"

AJAX :: XML and AJAX

AJAX can be used for interactive communication with an XML file.

AJAX XML Example

The following example will demonstrate how a web page can fetch information from an XML file with AJAX:

Example Explained - The HTML Page

When a user selects a CD in the dropdown list above, a function called "showCD()" is executed. The function is triggered by the "onchange" event:

<html>
<head>
<script type="text/javascript">
function showCD(str)
{
if (str=="")
{
document.getElementById("txtHint").innerHTML="";
return;
}
if (window.XMLHttpRequest)
{// code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp=new XMLHttpRequest();
}
else
{// code for IE6, IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.onreadystatechange=function()
{
if (xmlhttp.readyState==4 && xmlhttp.status==200)
    {
    document.getElementById("txtHint").innerHTML=xmlhttp.responseText;
    }
}
xmlhttp.open("GET","getcd.php?q="+str,true);
xmlhttp.send();
}
</script>
</head>
<body>

<form>
Select a CD:
<select name="cds" onchange="showCD(this.value)">
<option value="">Select a CD:</option>
<option value="Bob Dylan">Bob Dylan</option>
<option value="Bonnie Tyler">Bonnie Tyler</option>
<option value="Dolly Parton">Dolly Parton</option>
</select>
</form>
<div id="txtHint"><b>CD info will be listed here...</b></div>

</body>
</html>

The showCD() function does the following:

Check if a CD is selected
Create an XMLHttpRequest object
Create the function to be executed when the server response is ready
Send the request off to a file on the server
Notice that a parameter (q) is added to the URL (with the content of the dropdown list)

The PHP File

The page on the server called by the JavaScript above is a PHP file called "getcd.php".
The PHP script loads an XML document, "cd_catalog.xml", runs a query against the XML file, and returns the result as HTML:

<?php
$q=$_GET["q"];

$xmlDoc = new DOMDocument();
$xmlDoc->load("cd_catalog.xml");

$x=$xmlDoc->getElementsByTagName('ARTIST');

for ($i=0; $i<=$x->length-1; $i++)
{
//Process only element nodes
if ($x->item($i)->nodeType==1)
  {
  if ($x->item($i)->childNodes->item(0)->nodeValue == $q)
    {
    $y=($x->item($i)->parentNode);
    }
  }
}

$cd=($y->childNodes);

for ($i=0;$i<$cd->length;$i++)
{
//Process only element nodes
if ($cd->item($i)->nodeType==1)
  {
echo("<b>" . $cd->item($i)->nodeName . ":</b> ");
  echo($cd->item($i)->childNodes->item(0)->nodeValue);
  echo("<br />");
  }
}
?>

When the CD query is sent from the JavaScript to the PHP page, the following happens:

PHP creates an XML DOM object
Find all <artist> elements that matches the name sent from the JavaScript
Output the album information (send to the "txtHint" placeholder)

AJAX :: introduction

AJAX is about updating parts of a web page, without reloading the whole page.

What is AJAX?

AJAX = Asynchronous JavaScript and XML.
AJAX is a technique for creating fast and dynamic web pages.
AJAX allows web pages to be updated asynchronously by exchanging small amounts of data with the server behind the scenes. This means that it is possible to update parts of a web page, without reloading the whole page.
Classic web pages, (which do not use AJAX) must reload the entire page if the content should change.
Examples of applications using AJAX: Google Maps, Gmail, Youtube, and Facebook tabs.

How AJAX Works

AJAX is Based on Internet Standards

AJAX is based on internet standards, and uses a combination of:

XMLHttpRequest object (to exchange data asynchronously with a server)
JavaScript/DOM (to display/interact with the information)
CSS (to style the data)
XML (often used as the format for transferring data)

AJAX applications are browser- and platform-independent!

Google Suggest

AJAX was made popular in 2005 by Google, with Google Suggest.
Google Suggest is using AJAX to create a very dynamic web interface: When you start typing in Google's search box, a JavaScript sends the letters off to a server and the server returns a list of suggestions.

Sunday, 10 July 2011

PHP XML :: SimpleXML

SimpleXML handles the most common XML tasks and leaves the rest for other extensions.

What is SimpleXML?

SimpleXML is new in PHP 5. It is an easy way of getting an element's attributes and text, if you know the XML document's layout.

Compared to DOM or the Expat parser, SimpleXML just takes a few lines of code to read text data from an element.

SimpleXML converts the XML document into an object, like this:

Elements - Are converted to single attributes of the SimpleXMLElement object. When there's more than one element on one level, they're placed inside an array
Attributes - Are accessed using associative arrays, where an index corresponds to the attribute name
Element Data - Text data from elements are converted to strings. If an element has more than one text node, they will be arranged in the order they are found

SimpleXML is fast and easy to use when performing basic tasks like:

Reading XML files
Extracting data from XML strings
Editing text nodes or attributes

However, when dealing with advanced XML, like namespaces, you are better off using the Expat parser or the XML DOM.

Installation

As of PHP 5.0, the SimpleXML functions are part of the PHP core. There is no installation needed to use these functions.

Using SimpleXML

Below is an XML file:

<?xml version="1.0" encoding="ISO-8859-1"?>

<note>

<to>Tove</to>

<from>Jani</from>

<heading>Reminder</heading>

<body>Don't forget me this weekend!</body>

</note>

We want to output the element names and data from the XML file above.

Here's what to do:

Load the XML file
Get the name of the first element
Create a loop that will trigger on each child node, using the children() function
Output the element name and data for each child node

Example

<?php

$xml = simplexml_load_file("test.xml");

echo $xml->getName() . "<br />";

foreach($xml->children() as $child)

  {

  echo $child->getName() . ": " . $child . "<br />";

  }

?>

The output of the code above will be:

note

to: Tove

from: Jani

heading: Reminder

body: Don't forget me this weekend!

PHP XML :: DOM

What is DOM?

The W3C DOM provides a standard set of objects for HTML and XML documents, and a standard interface for accessing and manipulating them.

The W3C DOM is separated into different parts (Core, XML, and HTML) and different levels (DOM Level 1/2/3):

* Core DOM - defines a standard set of objects for any structured document
* XML DOM - defines a standard set of objects for XML documents
* HTML DOM - defines a standard set of objects for HTML documents

XML Parsing

To read and update - create and manipulate - an XML document, you will need an XML parser.

There are two basic types of XML parsers:

Tree-based parser: This parser transforms an XML document into a tree structure. It analyzes the whole document, and provides access to the tree elements
Event-based parser: Views an XML document as a series of events. When a specific event occurs, it calls a function to handle it

The DOM parser is an tree-based parser.

Look at the following XML document fraction:

<?xml version="1.0" encoding="ISO-8859-1"?>

<from>Jani</from>

The XML DOM sees the XML above as a tree structure:

Level 1: XML Document
Level 2: Root element: <from>
Level 3: Text element: "Jani"

Installation

The DOM XML parser functions are part of the PHP core. There is no installation needed to use these functions.

An XML File

The XML file below will be used in our example:

<?xml version="1.0" encoding="ISO-8859-1"?>

<note>

<to>Tove</to>

<from>Jani</from>

<heading>Reminder</heading>

<body>Don't forget me this weekend!</body>

</note>

Load and Output XML

We want to initialize the XML parser, load the xml, and output it:

Example

<?php

$xmlDoc = new DOMDocument();

$xmlDoc->load("note.xml");

print $xmlDoc->saveXML();

?>

The output of the code above will be:

Tove Jani Reminder Don't forget me this weekend!

If you select "View source" in the browser window, you will see the following HTML:

<?xml version="1.0" encoding="ISO-8859-1"?>

<note>

<to>Tove</to>

<from>Jani</from>

<heading>Reminder</heading>

<body>Don't forget me this weekend!</body>

</note>

The example above creates a DOMDocument-Object and loads the XML from "note.xml" into it.

Then the saveXML() function puts the internal XML document into a string, so we can output it.

Looping through XML

We want to initialize the XML parser, load the XML, and loop through all elements of the <note> element:

Example

<?php

$xmlDoc = new DOMDocument();

$xmlDoc->load("note.xml");

$x = $xmlDoc->documentElement;

foreach ($x->childNodes AS $item)

  {

  print $item->nodeName . " = " . $item->nodeValue . "<br />";

  }

?>

The output of the code above will be:

#text =

to = Tove

#text =

from = Jani

#text =

heading = Reminder

#text =

body = Don't forget me this weekend!

#text =

In the example above you see that there are empty text nodes between each element.

When XML generates, it often contains white-spaces between the nodes. The XML DOM parser treats these as ordinary elements, and if you are not aware of them, they sometimes cause problems.

PHP XML :: Introduction

The built-in Expat parser makes it possible to process XML documents in PHP.

What is XML?

XML is used to describe data and to focus on what data is. An XML file describes the structure of the data.

In XML, no tags are predefined. You must define your own tags.

What is Expat?

To read and update - create and manipulate - an XML document, you will need an XML parser.

There are two basic types of XML parsers:

Tree-based parser: This parser transforms an XML document into a tree structure. It analyzes the whole document, and provides access to the tree elements. e.g. the Document Object Model (DOM)
Event-based parser: Views an XML document as a series of events. When a specific event occurs, it calls a function to handle it

The Expat parser is an event-based parser.

Event-based parsers focus on the content of the XML documents, not their structure. Because of this, event-based parsers can access data faster than tree-based parsers.

Look at the following XML fraction:

<from>Jani</from>

An event-based parser reports the XML above as a series of three events:

Start element: from
Start CDATA section, value: Jani
Close element: from

The XML example above contains well-formed XML. However, the example is not valid XML, because there is no Document Type Definition (DTD) associated with it.

However, this makes no difference when using the Expat parser. Expat is a non-validating parser, and ignores any DTDs.

As an event-based, non-validating XML parser, Expat is fast and small, and a perfect match for PHP web applications.

Note: XML documents must be well-formed or Expat will generate an error.

Installation

The XML Expat parser functions are part of the PHP core. There is no installation needed to use these functions.

An XML File

The XML file below will be used in our example:

<?xml version="1.0" encoding="ISO-8859-1"?>

<note>

<to>Tove</to>

<from>Jani</from>

<heading>Reminder</heading>

<body>Don't forget me this weekend!</body>

</note>

Initializing the XML Parser

We want to initialize the XML parser in PHP, define some handlers for different XML events, and then parse the XML file.

Example

<?php

//Initialize the XML parser

$parser=xml_parser_create();

//Function to use at the start of an element

function start($parser,$element_name,$element_attrs)

  {

  switch($element_name)

    {

    case "NOTE":

    echo "-- Note --<br />";

    break;

    case "TO":

    echo "To: ";

    break;

    case "FROM":

    echo "From: ";

    break;

    case "HEADING":

    echo "Heading: ";

    break;

    case "BODY":

    echo "Message: ";

    }

  }

//Function to use at the end of an element

function stop($parser,$element_name)

  {

  echo "<br />";

  }

//Function to use when finding character data

function char($parser,$data)

  {

  echo $data;

  }

//Specify element handler

xml_set_element_handler($parser,"start","stop");

//Specify data handler

xml_set_character_data_handler($parser,"char");

//Open XML file

$fp=fopen("test.xml","r");

//Read data

while ($data=fread($fp,4096))

  {

  xml_parse($parser,$data,feof($fp)) or

  die (sprintf("XML Error: %s at line %d",

  xml_error_string(xml_get_error_code($parser)),

  xml_get_current_line_number($parser)));

  }

//Free the XML parser

xml_parser_free($parser);

?>

The output of the code above will be:

-- Note --

To: Tove

From: Jani

Heading: Reminder

Message: Don't forget me this weekend!

How it works:

Initialize the XML parser with the xml_parser_create() function
Create functions to use with the different event handlers
Add the xml_set_element_handler() function to specify which function will be executed when the parser encounters the opening and closing tags
Add the xml_set_character_data_handler() function to specify which function will execute when the parser encounters character data
Parse the file "test.xml" with the xml_parse() function
In case of an error, add xml_error_string() function to convert an XML error to a textual description
Call the xml_parser_free() function to release the memory allocated with the xml_parser_create() function