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Trackback Class

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The Trackback Class provides functions that enable you to send and receive Trackback data.

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If you are not familiar with Trackbacks you'll find more information here.

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Initializing the Class

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Like most other classes in CodeIgniter, the Trackback class is initialized in your controller using the $this->load->library function:

- -$this->load->library('trackback'); -

Once loaded, the Trackback library object will be available using: $this->trackback

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Sending Trackbacks

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A Trackback can be sent from any of your controller functions using code similar to this example:

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$this->load->library('trackback');

-

-$tb_data = array(

-                'ping_url'  => 'http://example.com/trackback/456',

-                'url'       => 'http://www.my-example.com/blog/entry/123',

-                'title'     => 'The Title of My Entry',

-                'excerpt'   => 'The entry content.',

-                'blog_name' => 'My Blog Name',

-                'charset'   => 'utf-8'

-                );

-

-if ( ! $this->trackback->send($tb_data))

-{

-     echo $this->trackback->display_errors();

-}

-else

-{

-     echo 'Trackback was sent!';

-}

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Description of array data:

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ping_url - The URL of the site you are sending the Trackback to. You can send Trackbacks to multiple URLs by separating each URL with a comma.
url - The URL to YOUR site where the weblog entry can be seen.
title - The title of your weblog entry.
excerpt - The content of your weblog entry. Note: the Trackback class will automatically send only the first 500 characters of your entry. It will also strip all HTML.
blog_name - The name of your weblog.
charset - The character encoding your weblog is written in. If omitted, UTF-8 will be used.

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The Trackback sending function returns TRUE/FALSE (boolean) on success or failure. If it fails, you can retrieve the error message using:

- -$this->trackback->display_errors(); - - -

Receiving Trackbacks

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Before you can receive Trackbacks you must create a weblog. If you don't have a blog yet there's no point in continuing.

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Receiving Trackbacks is a little more complex than sending them, only because you will need a database table in which to store them, -and you will need to validate the incoming trackback data. You are encouraged to implement a thorough validation process to -guard against spam and duplicate data. You may also want to limit the number of Trackbacks you allow from a particular IP within -a given span of time to further curtail spam. The process of receiving a Trackback is quite simple; -the validation is what takes most of the effort.

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Your Ping URL

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In order to accept Trackbacks you must display a Trackback URL next to each one of your weblog entries. This will be the URL -that people will use to send you Trackbacks (we will refer to this as your "Ping URL").

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Your Ping URL must point to a controller function where your Trackback receiving code is located, and the URL -must contain the ID number for each particular entry, so that when the Trackback is received you'll be -able to associate it with a particular entry.

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For example, if your controller class is called Trackback, and the receiving function is called receive, your -Ping URLs will look something like this:

- -http://example.com/index.php/trackback/receive/entry_id - -

Where entry_id represents the individual ID number for each of your entries.

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Creating a Trackback Table

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Before you can receive Trackbacks you must create a table in which to store them. Here is a basic prototype for such a table:

- - - - -

The Trackback specification only requires four pieces of information to be sent in a Trackback (url, title, excerpt, blog_name), -but to make the data more useful we've added a few more fields in the above table schema (date, IP address, etc.).

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Processing a Trackback

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Here is an example showing how you will receive and process a Trackback. The following -code is intended for use within the controller function where you expect to receive Trackbacks.

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$this->load->library('trackback');

-$this->load->database();

-

-if ($this->uri->segment(3) == FALSE)

-{

-    $this->trackback->send_error("Unable to determine the entry ID");

-}

-

-if ( ! $this->trackback->receive())

-{

-    $this->trackback->send_error("The Trackback did not contain valid data");

-}

-

-$data = array(

-                'tb_id'      => '',

-                'entry_id'   => $this->uri->segment(3),

-                'url'        => $this->trackback->data('url'),

-                'title'      => $this->trackback->data('title'),

-                'excerpt'    => $this->trackback->data('excerpt'),

-                'blog_name'  => $this->trackback->data('blog_name'),

-                'tb_date'    => time(),

-                'ip_address' => $this->input->ip_address()

-                );

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-$sql = $this->db->insert_string('trackbacks', $data);

-$this->db->query($sql);

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-$this->trackback->send_success();

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Notes:

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The entry ID number is expected in the third segment of your URL. This is based on the URI example we gave earlier:

- -http://example.com/index.php/trackback/receive/entry_id - -

Notice the entry_id is in the third URI segment, which you can retrieve using:

- -$this->uri->segment(3); - -

In our Trackback receiving code above, if the third segment is missing, we will issue an error. Without a valid entry ID, there's no -reason to continue.

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The $this->trackback->receive() function is simply a validation function that looks at the incoming data -and makes sure it contains the four pieces of data that are required (url, title, excerpt, blog_name). -It returns TRUE on success and FALSE on failure. If it fails you will issue an error message.

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The incoming Trackback data can be retrieved using this function:

- -$this->trackback->data('item') - -

Where item represents one of these four pieces of info: url, title, excerpt, or blog_name

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If the Trackback data is successfully received, you will issue a success message using:

- -$this->trackback->send_success(); - -

Note: The above code contains no data validation, which you are encouraged to add.

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CodeIgniter User Guide Version 2.0.3

Trackback Class

Initializing the Class

Sending Trackbacks

Receiving Trackbacks

Your Ping URL

Creating a Trackback Table

Processing a Trackback

Notes: