Simple Image CAPTCHA

Snippet Code

This is your most basic version of an image CAPTCHA.

image.php




<?php

header("Content-type: image/png");

$string = "abcdefghijklmnopqrstuvwxyz0123456789";

for($i=0;$i<6;$i++){

    $pos = rand(0,36);

    $str .= $string{$pos};

}



$img_handle = ImageCreate (60, 20) or die ("Cannot Create image");

//Image size (x,y)

$back_color = ImageColorAllocate($img_handle, 255, 255, 255);

//Background color RBG

$txt_color = ImageColorAllocate($img_handle, 0, 0, 0);

//Text Color RBG

ImageString($img_handle, 31, 5, 0, $str, $txt_color);

Imagepng($img_handle);



session_start();

$_SESSION['img_number'] = $str;

?>

form.php




<form action="result.php" method="post">

    <img alt="Random Number" src="image.php"> 

    <input type="text" name="num"><br>

    <input type="submit" name="submit" value="Check">

</form>

result.php




<?php

session_start();

if($_SESSION['img_number'] != $_POST['num']){

    echo'The number you entered doesn't match the image.<br>

    <a href="form.php">Try Again</a><br>';

}else{

    echo'The numbers Match!<br>

    <a href="form.php">Try Again</a><br>;

}

?>

Example

Snippet Comments

Add Your Comment

Gerry
2007-07-17 00:00:00

is there anyway of styling the image?

neilfurry
2007-10-10 00:00:00

well I think mr.anonymous doesnt know the real meaning of "SIMPLE", what he is trying to imply is an ADVANCE type of captcha...lol..

jl
2007-07-01 00:00:00

if you want to generate a new image everytime you visit the "form" page, use this in begining of "image" code:

header( "Cache-Control: no-store, no-cache, must-revalidate" );
header( "Cache-Control: post-check=0, pre-check=0", false );
header( "Pragma: nocache" );

Anonymous
2007-05-16 00:00:00

It is not secure at all. No random lines, no distorted text... heh. Even the most basic bot can crack this, no sweat.

Admin
2007-03-26 00:00:00

Well... Anonymous That is one reason it is called a "Simple Image CAPTCHA". It is simple and it works like the more fancy ones.

I will try to create a fancier one though for future reference.

SomaFM
2007-02-16 00:00:00

"Anonymous", when you post a comment like that you should expand on why you think that.

Anonymous
2007-02-22 00:00:00

Well, unlike most captchas, there aren't any lines or anything, difference in colors, or anything that makes it seem "secure".

Anonymous
2007-02-13 00:00:00

Doesn't look very secure.

Admin
2007-02-13 00:00:00

It depends on what you mean by "Look and Feel" Do you want the image to have different text?

g
2007-02-13 00:00:00

how can u modify the the look of the image?

Admin
2007-02-09 00:00:00

Your Very Welcome!

SomaFM
2007-02-09 00:00:00

Nevermind. session_unset() does the trick :) Thanks for the great code!

SomaFM
2007-02-09 00:00:00

Great code. But is there anyway to end the session so the person can't use the back button and use the same code again in the form? I've tried placing session_destroy(); in my image.php script right before it creates a session. Also, I tried placing it in the page that gets executed by the form.

Wondering
2007-02-08 00:00:00

Can we see an example of what the final captcha will look like?

Add Your Comment