PHP CAPTCHA, image validation script

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PHP Script Forums » PHP snippets and example code

PHP CAPTCHA, image validation

(3 posts)

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Started 1 month ago by Olaf
Latest reply from Olaf

Great offers for webmaster, blogger and web developer!

Olaf
PHP Coder

Use this script to protect your contact form, your whois query tool or just a form where some extra validation is needed. How does it work?
A session will be created inside a dynamic image file (requires GD library). The random value of this image appears inside the generated CAPTCHA image. The user has to enter this value into a form field. While processing the form, the entered value get checked against the session value. Without entering the correct string a form will not be processed. This mechanism is very useful to protect your form again (spam) bots.

The PHP code snippet

Create a php file with that code an call it "random.php"

<?php
session_start();
 
if (empty($_SESSION['rand_code'])) {
    $str = "";
    $length = 0;
    for ($i = 0; $i < 4; $i++) {
        // this numbers refer to numbers of the ascii table (small-caps)
        $str .= chr(rand(97, 122));
    }
    $_SESSION['rand_code'] = $str;
}
 
$imgX = 60;
$imgY = 20;
$image = imagecreatetruecolor(60, 20);
 
$backgr_col = imagecolorallocate($image, 238,239,239);
$border_col = imagecolorallocate($image, 208,208,208);
$text_col = imagecolorallocate($image, 46,60,31);
 
imagefilledrectangle($image, 0, 0, 60, 20, $backgr_col);
imagerectangle($image, 0, 0, 59, 19, $border_col);
 
$font = "VeraSe.ttf"; // it's a Bitstream font check <a href="http://www.gnome.org" rel="nofollow">http://www.gnome.org</a> for more
$font_size = 10;
$angle = 0;
$box = imagettfbbox($font_size, $angle, $font, $_SESSION['rand_code']);
$x = (int)($imgX - $box[4]) / 2;
$y = (int)($imgY - $box[5]) / 2;
imagettftext($image, $font_size, $angle, $x, $y, $text_col, $font, $_SESSION['rand_code']);
 
header("Content-type: image/png");
imagepng($image);
imagedestroy ($image);
?>

How-to use it?

Use this HTML code in your form:

<input type="text" name="validator" id="validator" size="4" />
<img src="random.php" alt="CAPTCHA image" align="top" />

This is the code to test the entered value:

if (!empty($_POST['validator']) &amp;&amp; $_POST['validator'] == $_SESSION['rand_code']) {
    // process your form here
    // at least destroy the session
    unset($_SESSION['rand_code']);
}

Posted 1 month ago #

melgurt
Member

Great script!! works well.. below where my improvements..it generates a new image on refresh now

Random.php
<?php
session_start();
$imgX = 60;
$imgY = 20;
$image = imagecreatetruecolor(60, 20);

$backgr_col = imagecolorallocate($image, 238,239,239);
$border_col = imagecolorallocate($image, 208,208,208);
$text_col = imagecolorallocate($image, 46,60,31);

imagefilledrectangle($image, 0, 0, 60, 20, $backgr_col);
imagerectangle($image, 0, 0, 59, 19, $border_col);

$font = "VeraSe.ttf"; // it's a Bitstream font check http://www.gnome.org for more
$font_size = 10;
$angle = 0;
$box = imagettfbbox($font_size, $angle, $font, $_SESSION['rand_code']);
$x = (int)($imgX - $box[4]) / 2;
$y = (int)($imgY - $box[5]) / 2;
imagettftext($image, $font_size, $angle, $x, $y, $text_col, $font, $_SESSION['rand_code']);

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

Signup.php
session_start();
unset($_SESSION['rand_code']);
if (empty($_SESSION['rand_code'])) {
$str = "";
$length = 0;
for ($i = 0; $i < 4; $i++) {
// this numbers refer to numbers of the ascii table (small-caps)
$str .= chr(rand(97, 122));
}
$_SESSION['rand_code'] = $str;
}
?>
<input type="text" name="validator" id="validator" size="4" />

Posted 1 week ago #
Olaf
PHP Coder

Hi,

thanks for the suggestion. I did the same in the beginning but changed it because I hate it to insert a new "string" if my form doesn't validate.
I use this button in my contact form for more than 2 years and never got spam (sure I got spam from humans).
May I ask you to edit your post to mention only the changed code? that makes it much easier for other users.

Posted 5 days ago #

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