generate a gif with text for deterrence

[stanza]

When you sign up for account in yahoo or gmail, they ask you to look at a gif file and type the letters from it. This seems to be useful for deterring hackers who write a bot to automatically sign up for many accounts.

Is it possible to do the same thing in php? If so, any existing libraries? Do I need to put any DLL for extending the PHP? (If not it's the best, because my site is hosted.)

Any other techniques for deterring malicious bots?

Thanks!

[NickCoons]

There are image-generating functions in PHP.. look them up at php.net and you will find a list of all of the supporting software that's needed. It's possible that your host already has these installed and configured, and all you'd have to do is write the script.

I've used these same functions to create weather buttons on-the-fly.. they work very well and are easy to use.

[ogletree]

DO a search for captcha or captcha php.

[hakre]

tell that guy the truth, it's in the pear package and all build-in-ready:
[pear.php.net...]

that should do the job even if it's alpha.

[mincklerstraat]

you know, David Sklar just gave a talk "11 Cool things to do with PHP", using PEAR CAPTCHA was one of the 11 cool things:

[sklar.com...]

[henry0]

mincklerstraat
very interesting link

now about part 1)?

is there a tutorial on generating those images
it uses a random (), some img create .... but where should I look to find more details about it?

thanks

[mincklerstraat]

For part 1, actually making the images, if I was doing it, since I'm lazy, I think I'd just copy the text in the link above and try it out, and once I get it working, try to incorporate it in my script somehow.

PHP gives you a bunch of options for random-ish types of numbers; a tutorial for doing this would introduce you to random numbers, introduce you to gd, things like imagettftext, imageline, and imagerotate; it'd show you how to figure out some parameters for limiting possible results so your image is as human-readable as possible, and as machine-unreadable as possible, 3 different things really.

The CAPTCHA people have done quite some work in trying to figure out the last bit, and I'd assume that the package makes use of their work so you don't have to go reinventing the wheel.

In David Sklar's example code, the only thing that immediately sticks out to me as something you'll want to change is the font name. You'll want to have this font installed in the correct directory - the PEAR CAPTCHA class docs should tell you where that's supposed to be, or maybe they just assume a relative uri from the calling script.

[henry0]

Thank you
I will check it out
I have no problem with random and others
but I should spend some time with GD

although the package sound a good deal!