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Creating a CAPTCHA with PHP :: PHP Tutorial

Tuesday, February 10, 15, 14:45:21, 8 Months Ago Via wain, Hits: 491
Captcha Image, This tutorial will show you how to create a form with Captcha.
1.Sessions in PHP are started by using the session_start() function. Like the setcookie( ) function, the session_start( ) function must come before any HTML, including blank lines, on the page.
<?php session_start(); ?>

2.Imagecreatefrompng :: create a new image from file or URL.
$img = imagecreatefrompng('black.png');

3.The function imagecolorallocate creates a color using RGB (red,green,blue) format.
$white = imagecolorallocate($img, 255, 255, 255);

4.Displaying the random text on the captcha image.
$numero = rand(100, 999);

5.Check if the security code and the session value are not blank and if the input text matches the stored text.
if(($_POST['check']) == $_SESSION['check'])
{ echo 'Input OK';
echo 'Input Wrong';



<form method="POST" action="cc.php">
<img src="captchas.php"> <br>
<input type="text" size="10" name="check"> <br>
<input type="submit" name="submit" value="submit">

<?php session_start();
//imagecreatefrompng :: create a new image
//from file or URL
$img = imagecreatefrompng('black.png');
//displaying the random text on the captcha
$numero = rand(100, 999);
$_SESSION['check'] = ($numero);
//The function imagecolorallocate creates a
//color using RGB (red,green,blue) format.
$white = imagecolorallocate($img, 255, 255, 255);
imagestring($img, 10, 8, 3, $numero, $white);
header ("Content-type: image/png"); imagepng($img);

//Sessions in PHP are started by using the
//session_start() function.
//Like the setcookie( ) function,
//the session_start function must come before any HTML,
//including blank lines, on the page.session_start();
//Check if the security code and
//the session value are not blank
//and if the input text matches the stored text
if(($_POST['check']) == $_SESSION['check']) {
echo 'Input OK';
echo 'Input Wrong';

example 2:


Svolte Monday, June 7, 2010, 16:32:25

Thanks a bunch for this script, its really helpful! :)

sivaramakrishnan Monday, July 12, 2010, 06:04:44

Nice,its very useful for me to creating it.

Alif Tuesday, July 27, 2010, 21:05:13

it's nice tutorial, thanks for share the code

Padmashri Friday, August 27, 2010, 06:14:39

Thanks for this php's very helpful for me.

Jeremy Wednesday, September 15, 2010, 09:06:24

thanks for this code ! Just how we can improve the security of this script and generally any captcha script ?

Mihail Tuesday, December 28, 2010, 14:52:12

nice tutorial,
//clear session to prevent re-use


//end of cc.php

jigibau Tuesday, December 28, 2010, 15:50:59

This is a very nice tutorial. Thanks ..

Michael Pedersen Wednesday, December 29, 2010, 10:21:04

Excellent script for beginners like me. I spend sooo much time on other scripts, but this one worked instantly.
Thanks a lot - Michael.

mimija Saturday, January 22, 2011, 05:41:49

Very useful tut, thank you :)

Ronald Paypon Sunday, February 27, 2011, 12:17:10

Simple but wonderful! Thanks a lot for this basic captcha code.

lakshitha Wednesday, March 2, 2011, 13:55:32

i got an issue pls help smone.. i did alert the session variable($_SESSION[\'check\']) in javascript but it alert the prvious captcha. not the current image captcha.(i got this issue whn i need to validate my form on js). here the code snippet

var imageVarification = $(\"#captcha\").val();
var imagecode = ;

lucky Saturday, March 19, 2011, 08:38:31

Thanks a lot!!! this was really helpful

micho Wednesday, May 4, 2011, 06:19:34

Great Tutorial... Thanks for Sharing.

will Tuesday, July 12, 2011, 11:36:02

Thanks for code also. It worked and was very helpful for me.

ronaldo Friday, August 12, 2011, 15:53:49

thanks admin

nero Wednesday, August 31, 2011, 18:14:04

Thanks for share the code

Michael Wednesday, October 12, 2011, 04:53:24

Very useful code, thanks much.

Gane Wednesday, December 28, 2011, 17:07:34

Thanks for this great tutorial, it was really usefull

Matthew Sunday, February 12, 2012, 18:39:24

Really useful bit of code, thanks for that.

blogger Wednesday, April 18, 2012, 11:28:49

Thanks for the very useful article.

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