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3.

In your

seophp/include

library, create a file named

simple_captcha.inc.php

, and then

type this code in:

<?php

// load Words library

require_once(‘Numbers/Words.php’);

// SimpleCAPTCHA library

class SimpleCAPTCHA

{

// verify answer

function check_answer($answer, $hash)

{

return (md5(trim($answer) . $_SERVER[‘SERVER_ADDR’]) == $hash);

}

// generate question

function get_question($max_1, $max_2)

{

// define standard question formats

$question_formats = array(

‘What is %s plus %s?’,

‘What is the sum of %s and %s?’,

‘What is %s added to %s?’,

‘What is %s + %s?’

);

// generate random numbers

$number_1 = rand(0, $max_1);

$number_2 = rand(0, $max_2);

// transforms the numbers to words

$number_1_words = Numbers_Words::toWords($number_1);

$number_2_words = Numbers_Words::toWords($number_2);

// generate a random question

$question = sprintf($question_formats[rand(0,

sizeof($question_formats) - 1)],

$number_1_words,

$number_2_words);

// returns the question and the hash of the result

return array(‘question’ => $question,

‘hash’ => md5(($number_1 + $number_2) . $_SERVER[‘SERVER_ADDR’]));

}

// generates demo form

function display_demo_form()

{

$gq = SimpleCAPTCHA::get_question(1000, 10);

echo ‘<form>’;

echo $gq[‘question’];

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Chapter 8: Black Hat SEO

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