Code: May 2016

CAPTCHA stands for “Completely Automated Public Turing test to tell Computers and Humans Apart”, it’s very common functionality to use at the time of submit data to prevent machines access of your website. In this post we will developed CAPTCHA script suing PHP with help of easy three steps.This is very basic captcha which is generated by PHP.

Following files will use in this Captcha Example

catpcha.jpg – A Image for catcha

captcha.php – This file is use to generate captcha with PHP using PHP session.

index.php – This file is use to show captcha image to end user.

Step 1

This image will used to generate captcha image using PHP GD library.This is a only dependency(GD library)

Step 2

We need to create a new file captcha.php

copy the code below in captcha.php

<?php

session_start();

header("Expires: Mon, 26 Jul 1997 05:00:00 GMT");

header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");

header("Cache-Control: no-store, no-cache, must-revalidate");

header("Cache-Control: post-check=0, pre-check=0", false);

header("Pragma: no-cache");

function _generateRandom($length=6)

{

$_rand_src = array(

array(48,57) //digits

, array(97,122) //lowercase chars

// , array(65,90) //uppercase chars

);

srand ((double) microtime() * 1000000);

$random_string = "";

for($i=0;$i<$length;$i++){

$i1=rand(0,sizeof($_rand_src)-1);

$random_string .= chr(rand($_rand_src[$i1][0],$_rand_src[$i1][1]));

}

return $random_string;

}

$im = @imagecreatefromjpeg("captcha.jpg");

$rand = _generateRandom(3);

$_SESSION['captcha'] = $rand;

ImageString($im, 5, 2, 2, $rand[0]." ".$rand[1]." ".$rand[2]." ", ImageColorAllocate ($im, 0, 0, 0));

$rand = _generateRandom(3);

ImageString($im, 5, 2, 2, " ".$rand[0]." ".$rand[1]." ".$rand[2], ImageColorAllocate ($im, 255, 0, 0));

Header ('Content-type: image/jpeg');

imagejpeg($im,NULL,100);

ImageDestroy($im);

?>

Step 3

We will create template file index.php

copy the code below in index.php

<h1>A Simple Example Of PHP CAPTCHA Script</h1>

<?php

if(isset($_POST["captcha"]))

if($_SESSION["captcha"]==$_POST["captcha"])

{

//CAPTHCA is valid; proceed the message: save to database, send by e-mail …

echo '<div class="alert alert-success">CAPTHCA is valid; proceed the message</div>';

}

else

{

echo '<div class="alert alert-danger">CAPTHCA is not valid; ignore submission</div>';

}

?>

<label for="email">Email address:</label>

</div>

<label for="pwd">Password:</label>

</div>

<div class="col-sm-5 pull-left"><label for="pwd">Anti Spam code, Please Enter 3 Black Symbols</label>

</div>

<button type="submit" class="btn btn-primary">Submit</button>

</div>

</form>

</div>

Code

Thursday, 5 May 2016

Script to create CAPTCHA in PHP

Monday, 2 May 2016

India Is The Top Source And Target Of Cyber Attacks

Blog Archive