Captcha image verification
posted on June 24, 2006, 12:47 amA good way to avoid automatic form submissions when creating a web form is to add some kind of verification. One of the best ways is to use an image verification, called also captcha. What it does is to dynamically create an image with a random string displayed on it. Then visitor is asked to type that string in a text field and once the form is submitted it checks if the string on the image matches the one inputted by the user. Because there is no easy way to read a text from an image (image recognition) this is a good way to protect your web forms from spammers.
For doing this CAPTCHA I would suggest using a session variable where you store the string generated and displayed on that dynamically generated image.
<?php session_start(); $text = rand(10000,99999); $_SESSION["vercode"] = $text; $height = 25; $width = 65; $image_p = imagecreate($width, $height); $black = imagecolorallocate($image_p, 0, 0, 0); $white = imagecolorallocate($image_p, 255, 255, 255); $font_size = 14; imagestring($image_p, $font_size, 5, 5, $text, $white); imagejpeg($image_p, null, 80); ?>
Save this code in a file called captcha.php. What this script does is to generate a random number from 10000 to 99999 and then assign it to $_SESSION['vercode']. Then it generates a 25x65 pixels image with black background and white text using size 14. So if you upload that captcha.php file on your web site and open http://www.site.com/captcha.php you will see an image displaying random integer. You will receive a new random integer every time you refresh that page.
Next we need to create our web form.
<form action="submit.php" method="post"> Comment: <textarea name="coment"></textarea><br> Enter Code <img src="captcha.php"><input type="text" name="vercode" /><br> <input type="submit" name="Submit" value="Submit" /> </form>
Above code will create a form with a single textarea box, randomly generated image using the captcha.php script and a text field where you will have to enter the verification code.
All we have to do now is to make the submit.php script which will check if the verification code you enter matches the one that has been randomly generated.
<?php session_start(); if ($_POST["vercode"] != $_SESSION["vercode"] OR $_SESSION["vercode"]=='') { echo '<strong>Incorrect verification code.</strong><br>'; } else { // add form data processing code here echo '<strong>Verification successful.</strong><br>'; }; ?>
Did you check our Contact Form script?
For a small fee we can make any of your web forms have a CAPTCHA verification. Let us know if you need help with it.
| Comments |
| Dimas posted on June 22, 2009, 6:39 pm |
| great tutor.. it works fine.. regards.. |
| Ketan posted on June 20, 2009, 4:32 pm |
| Very little code that is good. |
| dooodi posted on May 20, 2009, 11:56 am |
| thanks very much |
| paulius posted on May 13, 2009, 12:14 am |
| Is that working just on explorer? mozilla shows some junk |
| Ashwini posted on May 4, 2009, 3:45 pm |
| This code is superb. But i m facing some problem with this code. I already have php file for form submission and i am confuse where to put that submit.php file code in my php file. Because following code is there echo "<script>"; echo "self.location='thanks.html'"; echo "</script>"; Please guide me where to put that code in my php file. Thankx & Regards, Ashwini |
| wie bali posted on April 27, 2009, 12:46 pm |
| great scripts ...! thanks |
| Tony Cortes posted on April 20, 2009, 6:20 pm |
| I really like this captcha and I know I'm missing something simple, but after it's done verifying the characters, how do you get it to send the form contents to the processing page. Right now the action goes to the submit.php. The action I had before went to mail.php for processing. I'm been using the 3D Form because I like it's autorepsponder. Anyway, thanks for any help or suggestion you can offer. Feel free to contact me. |
| kyle posted on April 7, 2009, 7:31 pm |
| cant get the image to show, not sure where to post the verification script (inside the form or after the /form) http://www.kylenoyes.com/Frameset.html |
| nigel123 posted on March 31, 2009, 3:27 pm |
| Works okay now.... |
| nigel123 posted on March 31, 2009, 2:23 pm |
| I'm not seeing the image and when I test the captcha.php file I get this error Parse error: syntax error, unexpected T_VARIABLE in /home/p12asso/public_html/captcha.php on line 8 this is the captcha.php code <?php session_start(); $text = rand(10000,99999); $_SESSION["vercode"] = $text; $height = 25; $width = 65; $image_p = imagecreate($width, $height); $black = imagecolorallocate($image_p, 0, 0, 0); $white = imagecolorallocate($image_p, 255, 255, 255); $font_size = 14; imagestring($image_p, $font_size, 5, 5, $text, $white); imagejpeg($image_p, null, 80); ?> I have verified the GD Library is enabled. Any ideas? Thanks. |