CAPTCHA validation

[eluser]InsiteFX[/eluser]
1) Open your css stylesheet and add a new style class that suppresses the display of a particular class.
Add more for other form fields like email!

Code:

input.my-url {
    display: none;
}

2) Open your form and add a field named "my_url" near the submit button.

Code:

<input type="text" name="my_url" class="my-url" value="">

3) In your script which validates user input for the Contact form, evaluate the contents of $_POST['my_url']. It should be empty. The stylesheet should have suppressed display to humans, but a spam robot would most likely enter a value.

Code:

if( ! empty($this->input->post('my_url', TRUE)))
{
    // It must be an Will Smith iRobot!
}
else
{
    // The form was submited by a human.
}

You should always use xss_clean in form rules and input post data!