Capthca Driver - PHP example

Designing PHP-Based Solutions: Best Practice example from a Well House Consultants training course
More on Designing PHP-Based Solutions: Best Practice [link]

This example is described in the following article(s):
• Check your user is human. Have him retype a word in a graphic - [link]

If you're searching for a page where you can try this code, select here

This example references the following resources:
http://www.wellho.net/resources/ex.php4?item=h115/gruse.php
http://www.wellho.net/resources/ex.php4?item=h115/grgen.php
http://www.wellho.net/resources/linktous.html

Source code: gruse.php Module: H115


<?php

/* Provides a login capability where the web site visitor
is asked to copy back a word or string of characters that
are displayed in a graphic. This capability is known as
Captcha. */

/*
Page 1 - offer login
Page 2 - offer application form
Page 3 - logout

Files required ...
a) This file
b) grgen.php (generate the graphics)
c) appropriate TTF font files
*/

session_name("grd"); // keep apart from other session demos
session_start();

$current = $_SESSION[current];
if (! $current) $current = 0;

$fill = array();
$fill[errmsg] = "";
$fill[result] = "";

// Finish up from previous page
///////////////////////////////

switch ($current) {

case 0:         # Initialise
        $current = 1;
        break;

case 1:         # Check Input
        $cooked = strtoupper($_REQUEST[youtyped]);
        $cooked = preg_replace('/1/','I',$cooked);
        $cooked = preg_replace('/0/','O',$cooked);
        if ($cooked == $_SESSION[word]) {
                $current = 2;
        } else {
                $fill["errmsg"] = "That was NOT correct<br>";
        }
        break;

case 2:         # Live application
        if ($_REQUEST[action] == "logout") {
                $current = 3;
        } else {
                $fill[result] = "You entered <b>".
                htmlspecialchars(stripslashes($_REQUEST[said])).
                "</b><br><br>";
        }
        break;
        }

$_SESSION[current] = $current;
$fill["current"] = $current;
$fill["of"] = 3;

// Prepare for next page
////////////////////////

switch ($current) {

case 1:         # Prepare Graphic
        $length = rand(3,7);
        $string = "";
        for ($k=0; $k<$length; $k++) {
        $char = rand(1,26);
        $string .= substr("QWERTYUIOPASDFGHJKLZXCVBNM",$char-1,1);
        }
        $_SESSION["word"] = $string;
        $fill["instruct"] = "<img src=grgen.php>";
        $fill["form"] = "<form method=post>";
        $fill["form"] .= "<br>Please enter the word you see";
        $fill["form"] .= "<input name=youtyped size=8><br>";
        $fill["form"] .= "<input name=action type=submit>";
        $fill["form"] .= "</form>";
        break;

case 2:         # Offer live application
        $fill["instruct"] = "<font color=brown>You are logged in</font>";
        $fill["form"] = "<form method=post>";
        $fill["form"] .= "<br>Please enter a piece of text";
        $fill["form"] .= "<input name=said><br>";
        $fill["form"] .= "<input name=action type=submit>";
        $fill["form"] .= " or <input name=action type=submit value=logout>";
        $fill["form"] .= "</form>";
        break;
case 3:         # Log out
        session_destroy();
        $fill["instruct"] = "<font color=brown>You have logged out</font>";
        $fill["form"] = "<br><br>Link - <a href=$PHP_SELF>Restart demo</a><br>";
        $fill["form"] .= "Link - <a href=/>Home Page</a><br>";
        break;
        }
?>
<html>
<head>
<title>Demonstration of Capthca driver in PHP</title>
</head>
<body>
<h1>Logging in by typing text in a graphic</h1>
This is a demonstration (with full source code available) showing how you
can write / run a PHP application to get your users to validate their
presence by re-typing the text in a graphic. Such techniques are know as
<b>Captcha</b> (Completely Automated Public Turing Test to Tell
Computers and Humans Apart).<br>
<h2>Page <?= $fill[current] ?> of <?= $fill[of] ?></h2><br>
<?= $fill[result] ?>
<?= $fill[errmsg] ?>
<?= $fill[instruct] ?>
<?= $fill[form] ?>
<br><br><i>This demonstration provides a human-identifying login capability
via a graphic. Users are required to copy a string on 3 to 7 letters that
are displayed.  Although the strings offered are letters only and all upper
case, the code accepts lower case inputs, and also 0 for O and 1 for I.
<br><br>Once logged in, all you'll see will be an echo application -
this is a demonstration of the 'real' user identification technology.</i>
<hr>
Demonstration by <a href=http://www.grahamellis.co.uk>Graham Ellis</a> of
<a href=http://www.wellho.net>Well House Consultants</a><br><br>
Source code -
<a href=http://www.wellho.net/resources/ex.php4?item=h115/gruse.php>this page</a>
and
<a href=http://www.wellho.net/resources/ex.php4?item=h115/grgen.php>graphic
generator script</a> <br><br>
If you use the source code of this demonstration on your site, please
provide a link back to us. See
<a href=http://www.wellho.net/resources/linktous.html>here</a>
</body>
</html>

Learn about this subject

This module and example are covered on the following public courses:
* Deploying LAMP - Linux, Apache, MySQL, Perl/PHP
* Linux Web Server
* Learning to program in PHP
* PHP Programming
* Intermediate PHP - weekend course / hobby / club / leisure users
* PHP Programming
* Learning to program in PHP
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