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MISCELLANEOUS

Creating a CAPTCHA with PHP
By: Andrew Walsh
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  • Rating: 4 stars4 stars4 stars4 stars4 stars / 70
    2006-06-06

    Table of Contents:
  • Creating a CAPTCHA with PHP
  • How does a CAPTCHA work?
  • Creating the random text
  • Writing the text to the image
  • Check if the user entered the code correctly
  • Improvements and Conclusion

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    Creating a CAPTCHA with PHP


    (Page 1 of 6 )

    In this tutorial, you will learn how to creat a CAPTCHA utilizing the graphics capabilities of PHP.

    You may be thinking just exactly what is a captcha? Well you are likely to have already seen them across the web. They are those little images with a code on the front that you type into a box in order to submit something. This kind of system helps to prevent automatic submitting of an operation by some kind of program or robot. In this tutorial I will show you how to make a CAPTCHA just like the one below. Its not the most advanced captcha available because it uses a simple system font and nothing more.

    The lines that you see above are to make any robots job of trying to work out that code a little harder. The dots in the background also help with this. I will now show you how to create one of these that uses a background file that you can easily change.

    More Miscellaneous Articles
    More By Andrew Walsh


       · The Text: As you can see from the code above we are loading the basic image from...
       · Ok it will be corrected soon
       · My bad...I fixed this yesterday...
       · I have been meaning to get a Captcha image installed on my little application. As...
       · Can i use this code to play around and use it in a wordpress (http://wordpress.org)...
       · Problem to use in Post nukewhen i impliment the captcha on post nuke web then i...
       · You can do what you like with it, although i thought wordpress included a much...
       · By changing this line:$string = substr($md5,0,5);With the following gives you...
       · By changing this line:$string = substr($md5,0,5);With the following gives you...
       · I get a problem that dont show the picture it shows alot of strange text...
       · <?php//Start the session so we can store what the code actually...
       · This was the base of the new captcha I made, except I did things a little...
       · please add this to the headers partheader("Cache-Control: no-cache,...
       · All goes well on a new page but I get this message when I incorporate it in an...
       · I get the same error when I don't start the session above the <html> tags,...
       · The site http://www.trycaptcha.com lets you try a bunch of open source CAPTCHA...
       · This tutorial really helped me out, thanks for the source!
       · Thanks for helpful little tutorial on how to do CAPTCHA! Never had to think about it...
       · The code would be great at prevent bots, but it has a critical flaw that would let...
       · please give me captcha work
       · You can this code to wordpresss also
     

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