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scheme is an alternative recording of the same information. This is used to overcome the usability

issues presented by CAPTCHA.

As a more simple but effective example, in the following exercise you create a small library that asks

simple math questions with random operands. Call it

SimpleCAPTCHA

.

Using SimpleCAPTCHA

1.

Start off by installing a required external library. Numbers_Words is a PEAR library that trans-

forms numbers to words, and you’re using it to make it harder for an automated script to parse

your forms and calculate the results. The official page of the package is

http://pear.php.net/package/Numbers_Words

.

PEAR offers a simple installation script. Open a command-line editor in the folder that contains

pear.php

. If you’re using XAMPP as instructed in Chapter 1, the folder will be

\Program

Files\xampp\php

. To browse to that folder using a command-line console, type this command:

cd \Program Files\xampp\php

At this moment your command-line console will look as shown in Figure 8-10.

Figure 8-10

2.

To install the Numbers_Words package, you need to execute this command:

pear install Numbers_Words

If the Numbers_Words package hasn’t reached a stable version (as is the case at the moment of

writing this chapter), you need to explicitly mention the beta version that you want to install,

like this:

pear install channel://pear.php.net/Numbers_Words-0.15.0

You should get a package confirmation message such as the following:

>pear install channel://pear.php.net/Numbers_Words-0.15.0

downloading Numbers_Words-0.15.0.tgz ...

Starting to download Numbers_Words-0.15.0.tgz (44,854 bytes)

............done: 44,854 bytes

install ok: channel://pear.php.net/Numbers_Words-0.15.0

At this point you can close the command-line console.

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Chapter 8: Black Hat SEO

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