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CAPTCHA Helper
##############

The CAPTCHA Helper file contains functions that assist in creating
CAPTCHA images.

.. contents:: Page Contents

Loading this Helper
===================

This helper is loaded using the following code
::

	$this->load->helper('captcha');

The following functions are available:

create_captcha()
================

.. php:function:: function create_captcha($data = '', $img_path = '', $img_url = '', $font_path = '')

	:param	array	$data: Array of data for the CAPTCHA
	:param	string	$img_path: Path to create the image in
	:param	string	$img_url: URL to the CAPTCHA image folder
	:param	string	$font_path: Server path to font
	:returns:	array('word' => $word, 'time' => $now, 'image' => $img)

Takes an array of information to generate the CAPTCHA as input and
creates the image to your specifications, returning an array of
associative data about the image.

::

	array(
		'image'	=> IMAGE TAG
		'time'	=> TIMESTAMP (in microtime)
		'word'	=> CAPTCHA WORD
	)

The **image** is the actual image tag::

	<img src="http://example.com/captcha/12345.jpg" width="140" height="50" />

The **time** is the micro timestamp used as the image name without the
file extension. It will be a number like this: 1139612155.3422

The **word** is the word that appears in the captcha image, which if not
supplied to the function, will be a random string.

Using the CAPTCHA helper
------------------------

Once loaded you can generate a captcha like this::

	$vals = array(
		'word'		=> 'Random word',
		'img_path'	=> './captcha/',
		'img_url'	=> 'http://example.com/captcha/',
		'font_path'	=> './path/to/fonts/texb.ttf',
		'img_width'	=> '150',
		'img_height'	=> 30,
		'expiration'	=> 7200,
		'word_length'	=> 8,
		'pool'	=> '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'
	);

	$cap = create_captcha($vals);
	echo $cap['image'];

-  The captcha function requires the GD image library.
-  Only the **img_path** and **img_url** are required.
-  If a **word** is not supplied, the function will generate a random
   ASCII string. You might put together your own word library that you
   can draw randomly from.
-  If you do not specify a path to a TRUE TYPE font, the native ugly GD
   font will be used.
-  The "captcha" folder must be writable (666, or 777)
-  The **expiration** (in seconds) signifies how long an image will remain
   in the captcha folder before it will be deleted. The default is two
   hours.
-  **word_length** defaults to 8, **pool** defaults to '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'

Adding a Database
-----------------

In order for the captcha function to prevent someone from submitting,
you will need to add the information returned from ``create_captcha()``
to your database. Then, when the data from the form is submitted by
the user you will need to verify that the data exists in the database
and has not expired.

Here is a table prototype::

	CREATE TABLE captcha (  
		captcha_id bigint(13) unsigned NOT NULL auto_increment,  
		captcha_time int(10) unsigned NOT NULL,  
		ip_address varchar(45) NOT NULL,  
		word varchar(20) NOT NULL,  
		PRIMARY KEY `captcha_id` (`captcha_id`),  
		KEY `word` (`word`)
	);

Here is an example of usage with a database. On the page where the
CAPTCHA will be shown you'll have something like this::

	$this->load->helper('captcha');
	$vals = array(     
		'img_path'	=> './captcha/',     
		'img_url'	=> 'http://example.com/captcha/'     
	);

	$cap = create_captcha($vals);
	$data = array(     
		'captcha_time'	=> $cap['time'],     
		'ip_address'	=> $this->input->ip_address(),     
		'word'		=> $cap['word']     
	);

	$query = $this->db->insert_string('captcha', $data);
	$this->db->query($query);

	echo 'Submit the word you see below:';
	echo $cap['image']; 
	echo '<input type="text" name="captcha" value="" />';

Then, on the page that accepts the submission you'll have something like
this::

	// First, delete old captchas
	$expiration = time() - 7200; // Two hour limit
	$this->db->where('captcha_time < ', $expiration)
		->delete('captcha');

	// Then see if a captcha exists:
	$sql = 'SELECT COUNT(*) AS count FROM captcha WHERE word = ? AND ip_address = ? AND captcha_time > ?';
	$binds = array($_POST['captcha'], $this->input->ip_address(), $expiration);
	$query = $this->db->query($sql, $binds);
	$row = $query->row();

	if ($row->count == 0)
	{     
		echo 'You must submit the word that appears in the image.';
	}