Thursday, August 11, 2011

PHP Example - AJAX Poll

AJAX Poll

The following example will demonstrate a poll where the result is shown without reloading.

Do you like PHP and AJAX so far?

Yes:
No:

Example Explained - The HTML Page

When a user choose an option above, a function called "getVote()" is executed. The function is triggered by the "onclick" event:








Do you like PHP and AJAX so far?



Yes:


No:





The getVote() function does 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 (vote) is added to the URL (with the value of the yes or no option)

The PHP File

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



Result:











Yes:

%
No:

%

The value is sent from the JavaScript, and the following happens:

  1. Get the content of the "poll_result.txt" file
  2. Put the content of the file in variables and add one to the selected variable
  3. Write the result to the "poll_result.txt" file
  4. Output a graphical representation of the poll result

The Text File

The text file (poll_result.txt) is where we store the data from the poll.

It is stored like this:

0||0

The first number represents the "Yes" votes, the second number represents the "No" votes.

Note: Remember to allow your web server to edit the text file. Do NOT give everyone access, just the web server (PHP).
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PHP Example - AJAX RSS Reader

An RSS Reader is used to read RSS Feeds.


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:












RSS-feed will be listed here...


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":

load($xml);

//get elements from ""
$channel=$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 ""
echo("

" . $channel_title . "");
echo("
");
echo($channel_desc . "

");

//get and output "" 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 ("

" . $item_title . "");
echo ("
");
echo ($item_desc . "

");
}
?>

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
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PHP Example - 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

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:













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:

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="" .
$y->item(0)->childNodes->item(0)->nodeValue . "";
}
else
{
$hint=$hint . "
" .
$y->item(0)->childNodes->item(0)->nodeValue . "";
}
}
}
}
}

// 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 elements to find matches from the text sent from the JavaScript</li><li>Sets the correct url and title in the "$response" variable. If more than one match is found, all matches are added to the variable</li><li>If no matches are found, the $response variable is set to "no suggestion"</li></ul></span></div>
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PHP Example - AJAX and XML

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

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:








Select a CD:


CD info will be listed here...



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:

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("" . $cd->item($i)->nodeName . ": ");
echo($cd->item($i)->childNodes->item(0)->nodeValue);
echo("
");
}
}
?>

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

  1. PHP creates an XML DOM object
  2. Find all elements that matches the name sent from the JavaScript
  3. Output the album information (send to the "txtHint" placeholder)
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PHP - AJAX and MySQL

AJAX can be used for interactive communication with a database.

Example Explained - The HTML Page

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












Person info will be listed here.



The showUser() function does the following:

  • Check if a person 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 "getuser.php".

The source code in "getuser.php" runs a query against a MySQL database, and returns the result in an HTML table:

";

while($row = mysql_fetch_array($result))
{
echo "";
echo "";
echo "";
echo "";
echo "";
echo "";
echo "";
}
echo "
0
if (strlen($q) > 0)
{
$hint="";
for($i=0; $i

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

  1. Find a name matching the characters sent from the JavaScript
  2. If no match were found, set the response string to "no suggestion"
  3. If one or more matching names were found, set the response string to all these names
  4. The response is sent to the "txtHint" placeholder
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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

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)

lamp AJAX applications are browser- and platform-independent!
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Wednesday, August 10, 2011

PHP 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:



Tove
Jani
Reminder
Don't forget me this weekend!

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

Here's what to do:

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

Example

getName() . "
";

foreach($xml->children() as $child)
{
echo $child->getName() . ": " . $child . "
";
}
?>

The output of the code above will be:

note
to: Tove
from: Jani
heading: Reminder
body: Don't forget me this weekend!
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PHP XML DOM

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

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

If you want to learn more about the XML DOM, please visit our XML DOM tutorial.

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:


Jani

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

  • Level 1: XML Document
  • Level 2: Root element:
  • 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:



Tove
Jani
Reminder
Don't forget me this weekend!

Load and Output XML

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

Example

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:



Tove
Jani
Reminder
Don't forget me this weekend!

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 element:

Example

load("note.xml");

$x = $xmlDoc->documentElement;
foreach ($x->childNodes AS $item)
{
print $item->nodeName . " = " . $item->nodeValue . "
";
}
?>

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.
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PHP XML Expat Parser

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:

Jani

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:



Tove
Jani
Reminder
Don't forget me this weekend!

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

CompanynameContactname
$compname$conname
";
?>


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