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

Loading this Helper

This helper is loaded using the following code:


Using the CAPTCHA helper

Once loaded you can generate a CAPTCHA like this:

$vals = array(
        'word'          => 'Random word',
        'img_path'      => './captcha/',
        'img_url'       => '',
        'font_path'     => './path/to/fonts/texb.ttf',
        'img_width'     => '150',
        'img_height'    => 30,
        'expiration'    => 7200,
        'word_length'   => 8,
        'font_size'     => 16,
        'img_id'        => 'Imageid',
        'pool'          => '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ',

        // White background and border, black text and red grid
        'colors'        => array(
                'background' => array(255, 255, 255),
                'border' => array(255, 255, 255),
                'text' => array(0, 0, 0),
                'grid' => array(255, 40, 40)

$cap = create_captcha($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” directory must be writable
  • 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’
  • font_size defaults to 16, the native GD font has a size limit. Specify a “true type” font for bigger sizes.
  • The img_id will be set as the “id” of the captcha image.
  • If any of the colors values is missing, it will be replaced by the default.

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:

$vals = array(
        'img_path'      => './captcha/',
        'img_url'       => ''

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

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

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)

// 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.';

Available Functions

The following functions are available:

create_captcha([$data = ''[, $img_path = ''[, $img_url = ''[, $font_path = '']]]])
  • $data (array) – Array of data for the CAPTCHA
  • $img_path (string) – Path to create the image in
  • $img_url (string) – URL to the CAPTCHA image folder
  • $font_path (string) – Server path to font

array(‘word’ => $word, ‘time’ => $now, ‘image’ => $img)

Return type:


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.

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

The image is the actual image tag:

<img src="" 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.