Creating custom captcha in PHP

Question

I want to create my custom Captcha validation in PHP and I have wrote this code but it doesn't seem to be working. The image is not being created and I cannot find where the error is.

PHP:

<?php
session_start();

$string = '';

for ($i = 0; $i < 5; $i++) {
    // this numbers refer to numbers of the ascii table (lower case)
    $string .= chr(rand(97, 122));
}

$_SESSION['rand_code'] = $string;

//specify the path where the font exists
$dir = 'fonts/arial.ttf';

$image = imagecreatetruecolor(170, 60);
$black = imagecolorallocate($image, 0, 0, 0);
$color = imagecolorallocate($image, 200, 100, 90); // red
$white = imagecolorallocate($image, 255, 255, 255);

imagefilledrectangle($image,0,0,399,99,$white);
imagettftext ($image, 30, 0, 10, 40, $color, $dir."arial.ttf", $_SESSION['random_code']);

header("Content-type: image/png");
imagepng($image);
?>

HTML:

<form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="post" enctype="multipart/form-data">
<p><input type="text" name="name" /> Name</p>
<p><input type="text" name="email" /> Email</p>
<p><textarea name="message"></textarea></p>
<img src="captcha.php"/>
<p><input type="text" name="code" /> Are you human?</p>
<p><input type="submit" name="submit" value="Send" class="button" /></p>
</form>

This calls for basic debugging. What goes wrong exactly? Are you getting an image? If not, remove the header() call and see what error messages come up. — Pekka
– Pekka, Commented Dec 3, 2013 at 22:30
No i'm not getting an image. I'm getting the default browser icon for a missing image. Removing the header() neither changed anything nor shown any error messages. — Smolikas
– Smolikas, Commented Dec 3, 2013 at 22:42
Use a library. This is likely a security feature you're enabling and it's best to use a known library rather than write your own. (unless of course you're writing an improved library) — Revan
– Revan, Commented Dec 3, 2013 at 23:20

Philipp · Accepted Answer · 2013-12-03 22:47:18Z

1

you generate a warning because of an undefined var..

change this line

imagettftext ($image, 30, 0, 10, 40, $color, $dir."arial.ttf", $_SESSION['random_code']);

to this one

imagettftext ($image, 30, 0, 10, 40, $color, $dir."arial.ttf", $_SESSION['rand_code']);

also check, if the font file is really available and readable, or you also will get an warning

answered Dec 3, 2013 at 22:47

Philipp

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1 Comment

Smolikas Over a year ago

Oh God. Thank you so much. That was the case. The undefined var i was accidentally miss-typed.

The Blue Dog · Accepted Answer · 2013-12-03 22:42:08Z

1

Change this:

imagettftext ($image, 30, 0, 10, 40, $color, $dir."arial.ttf", $_SESSION['random_code']);

To this:

imagettftext ($image, 30, 0, 10, 40, $color, $dir, $_SESSION['random_code']);

You're already setting the font file name here:

$dir = 'fonts/arial.ttf';

answered Dec 3, 2013 at 22:42

The Blue Dog

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Smolikas Over a year ago

Yes, i just found that out too and i changed it, but still nothing happened.

David · Accepted Answer · 2013-12-03 22:45:45Z

0

This is a jquery validate captcha?

1.- Do you have GD library installed?

2.- The file is named .php or .jpg? If is named .jpg, your server can execute .jpg files like a .php files?

Other recomendation. Are you trying HoneyPot validation instead of captcha?

answered Dec 3, 2013 at 22:45

David

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Comments

Carlos Robles · Accepted Answer · 2013-12-03 22:59:33Z

0

first, change the text from the session var to some hardcoded string,something like

imagettftext ($image, 30, 0, 10, 40, $color, $dir , "sdfsfdsfd");

If still not working, remove the line

header("Content-type: image/png");

and open the complete URL of captcha.php in your browser. it will display some errors for sure.

answered Dec 3, 2013 at 22:59

Carlos Robles

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1 Comment

Carlos Robles Over a year ago

sorry, i was writing and I forget to post it, when i did, in the mean time you already had found the answer! my bad!

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