PHP - AJAX and PHP

AJAX is used to create more interactive applications.

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

Start typing a name in the input field below: First name: Suggestions:

Source code explanation:

If the input field is empty (str.length==0), the function clears the content of the txtHint placeholder and exits the function.

If the input field is not empty, the showHint() 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)

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The PHP File

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

The source code in "gethint.php" checks an array of names, and returns the corresponding name(s) to the browser:

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

AJAX Introduction

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

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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.

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How AJAX Works

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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!

PHP SimpleXML

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

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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.

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Installation

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

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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!

PHP XML DOM

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

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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.

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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"

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Installation

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

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An XML File

The XML file below will be used in our example:

Tove Jani Reminder Don't forget me this weekend!

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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.

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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.

PHP XML Expat Parser

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

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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.

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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.

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Installation

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

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An XML File

The XML file below will be used in our example:

Tove Jani Reminder Don't forget me this weekend!

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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

Companyname	Contactname
$compname	$conname

";
?>

PHP MySQL Delete

The DELETE statement is used to delete records in a table.

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Delete Data In a Database

The DELETE FROM statement is used to delete records from a database table.

Syntax

DELETE FROM table_name WHERE some_column = some_value

Note: Notice the WHERE clause in the DELETE syntax. The WHERE clause specifies which record or records that should be deleted. If you omit the WHERE clause, all records will be deleted!

To get PHP to execute the statement above we must use the mysql_query() function. This function is used to send a query or command to a MySQL connection.

Example

Look at the following "Persons" table:

FirstName	LastName	Age
Peter	Griffin	35
Glenn	Quagmire	33

The following example deletes all the records in the "Persons" table where LastName='Griffin':

After the deletion, the table will look like this:

FirstName	LastName	Age
Glenn	Quagmire	33