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| <h1>Trackback Class</h1> | |
| <p>The Trackback Class provides functions that enable you to send and receive Trackback data.</p> | |
| <p>If you are not familiar with Trackbacks you'll find more information <a href="http://en.wikipedia.org/wiki/Trackback">here</a>.</p> | |
| <h2>Initializing the Class</h2> | |
| <p>Like most other classes in CodeIgniter, the Trackback class is initialized in your controller using the <dfn>$this->load->library</dfn> function:</p> | |
| <code>$this->load->library('trackback');</code> | |
| <p>Once loaded, the Trackback library object will be available using: <dfn>$this->trackback</dfn></p> | |
| <h2>Sending Trackbacks</h2> | |
| <p>A Trackback can be sent from any of your controller functions using code similar to this example:</p> | |
| <code>$this->load->library('trackback');<br /> | |
| <br /> | |
| $tb_data = array(<br /> | |
| 'ping_url' => 'http://example.com/trackback/456',<br /> | |
| 'url' => 'http://www.my-example.com/blog/entry/123',<br /> | |
| 'title' => 'The Title of My Entry',<br /> | |
| 'excerpt' => 'The entry content.',<br /> | |
| 'blog_name' => 'My Blog Name',<br /> | |
| 'charset' => 'utf-8'<br /> | |
| );<br /> | |
| <br /> | |
| if ( ! $this->trackback->send($tb_data))<br /> | |
| {<br /> | |
| echo $this->trackback->display_errors();<br /> | |
| }<br /> | |
| else<br /> | |
| {<br /> | |
| echo 'Trackback was sent!';<br /> | |
| }</code> | |
| <p>Description of array data:</p> | |
| <ul> | |
| <li><strong>ping_url</strong> - The URL of the site you are sending the Trackback to. You can send Trackbacks to multiple URLs by separating each URL with a comma.</li> | |
| <li><strong>url</strong> - The URL to YOUR site where the weblog entry can be seen.</li> | |
| <li><strong>title</strong> - The title of your weblog entry.</li> | |
| <li><strong>excerpt</strong> - The content of your weblog entry. Note: the Trackback class will automatically send only the first 500 characters of your entry. It will also strip all HTML.</li> | |
| <li><strong>blog_name</strong> - The name of your weblog.</li> | |
| <li><strong>charset</strong> - The character encoding your weblog is written in. If omitted, UTF-8 will be used.</li> | |
| </ul> | |
| <p>The Trackback sending function returns TRUE/FALSE (boolean) on success or failure. If it fails, you can retrieve the error message using:</p> | |
| <code>$this->trackback->display_errors();</code> | |
| <h2>Receiving Trackbacks</h2> | |
| <p>Before you can receive Trackbacks you must create a weblog. If you don't have a blog yet there's no point in continuing.</p> | |
| <p>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.</p> | |
| <h2>Your Ping URL</h2> | |
| <p>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").</p> | |
| <p>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.</p> | |
| <p>For example, if your controller class is called <dfn>Trackback</dfn>, and the receiving function is called <dfn>receive</dfn>, your | |
| Ping URLs will look something like this:</p> | |
| <code>http://www.your-site.com/index.php/trackback/receive/<samp>entry_id</samp></code> | |
| <p>Where <samp>entry_id</samp> represents the individual ID number for each of your entries.</p> | |
| <h2>Creating a Trackback Table</h2> | |
| <p>Before you can receive Trackbacks you must create a table in which to store them. Here is a basic prototype for such a table:</p> | |
| <textarea class="textarea" style="width:100%" cols="50" rows="13"> | |
| CREATE TABLE trackbacks ( | |
| tb_id int(10) unsigned NOT NULL auto_increment, | |
| entry_id int(10) unsigned NOT NULL default 0, | |
| url varchar(200) NOT NULL, | |
| title varchar(100) NOT NULL, | |
| excerpt text NOT NULL, | |
| blog_name varchar(100) NOT NULL, | |
| tb_date int(10) NOT NULL, | |
| ip_address varchar(16) NOT NULL, | |
| PRIMARY KEY (tb_id), | |
| KEY (entry_id) | |
| );</textarea> | |
| <p>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.).</p> | |
| <h2>Processing a Trackback</h2> | |
| <p>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.</p> | |
| <code>$this->load->library('trackback');<br /> | |
| $this->load->database();<br /> | |
| <br /> | |
| if ($this->uri->segment(3) == FALSE)<br /> | |
| {<br /> | |
| $this->trackback->send_error("Unable to determine the entry ID");<br /> | |
| }<br /> | |
| <br /> | |
| if ( ! $this->trackback->receive())<br /> | |
| {<br /> | |
| $this->trackback->send_error("The Trackback did not contain valid data");<br /> | |
| }<br /> | |
| <br /> | |
| $data = array(<br /> | |
| 'tb_id' => '',<br /> | |
| 'entry_id' => $this->uri->segment(3),<br /> | |
| 'url' => $this->trackback->data('url'),<br /> | |
| 'title' => $this->trackback->data('title'),<br /> | |
| 'excerpt' => $this->trackback->data('excerpt'),<br /> | |
| 'blog_name' => $this->trackback->data('blog_name'),<br /> | |
| 'tb_date' => time(),<br /> | |
| 'ip_address' => $this->input->ip_address()<br /> | |
| );<br /> | |
| <br /> | |
| $sql = $this->db->insert_string('trackbacks', $data);<br /> | |
| $this->db->query($sql);<br /> | |
| <br /> | |
| $this->trackback->send_success();</code> | |
| <h4>Notes:</h4> | |
| <p>The entry ID number is expected in the third segment of your URL. This is based on the URI example we gave earlier:</p> | |
| <code>http://www.your-site.com/index.php/trackback/receive/<samp>entry_id</samp></code> | |
| <p>Notice the entry_id is in the third URI, which you can retrieve using:</p> | |
| <code>$this->uri->segment(3);</code> | |
| <p>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.</p> | |
| <p>The <dfn>$this->trackback->receive()</dfn> function is simply a validation function that looks at the incoming data | |
| and makes sure it contains the four pieces of data that are required (url, title, excerpt, blog_name). | |
| It returns TRUE on success and FALSE on failure. If it fails you will issue an error message.</p> | |
| <p>The incoming Trackback data can be retrieved using this function:</p> | |
| <code>$this->trackback->data('<var>item</var>')</code> | |
| <p>Where <var>item</var> represents one of these four pieces of info: url, title, excerpt, or blog_name</p> | |
| <p>If the Trackback data is successfully received, you will issue a success message using:</p> | |
| <code>$this->trackback->send_success();</code> | |
| <p class="important"><strong>Note:</strong> The above code contains no data validation, which you are encouraged to add.</p> | |
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