Results 1 to 2 of 2

Thread: Simple CAPTCHA Verification Form

  1. #1
    mega's Avatar
    mega is offline Newbie Net Builder
    Join Date
    May 2009
    Location
    Hell , Wanna Come ??
    Posts
    62
    Thanks
    0
    Thanked 10 Times in 4 Posts

    Simple CAPTCHA Verification Form

    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.
    Code:
     
    
    <? 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[&#39;vercode&#39;]. 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 openhttp://www.yoursite.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.
    Code:
    <form action="submit.php" method="post"> Comment: <textarea name="coment"></textarea> Enter Code [img]captcha.php[/img]<input type="text" name="vercode" /> <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.
    Code:
    <? session_start(); if ($_POST["vercode"] != $_SESSION["vercode"] OR $_SESSION["vercode"]==&#39;&#39;) { echo &#39;Incorrect verification code. &#39;; } else { // add form data processing code here echo &#39;Verification successful. &#39;; }; ?>
    This is a great source for those web developers combating the dreaded spambots.
    Never argue with an idiot; First he takes you down to his level and then he beats you with experience.

  2. Thanked by:

    Aziz (25 October, 2009), ruben (18 October, 2009), Sami4u (10 November, 2009)

  3. #2
    ruben's Avatar
    ruben is offline Net Builder
    Join Date
    Oct 2009
    Posts
    378
    Blog Entries
    1
    Thanks
    44
    Thanked 57 Times in 48 Posts
    I like it mate but can you add something to the code so the text appears on a lined background and with a weird font

Similar Threads

  1. PHP Form verification: preg or built in functions
    By DickTracy in forum Programming
    Replies: 4
    Last Post: 13 December, 2009, 09:46 AM
  2. Foreign Keyboards + Captcha
    By Kovich in forum Tech-Talk
    Replies: 3
    Last Post: 5 October, 2009, 16:11 PM
  3. [WTS] contact form script with nice captcha
    By chandan in forum Scripts
    Replies: 0
    Last Post: 25 September, 2009, 06:19 AM
  4. PayPal Verification with a VCC
    By sivasriram in forum Business
    Replies: 14
    Last Post: 31 July, 2009, 09:08 AM

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •