Is this possible with PHP, a random signature?

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gnomes
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Is this possible with PHP, a random signature?

Postby gnomes » Mon Sep 17, 2007 9:46 pm UTC

I just thought about it, would it be possible to have a php file grab a random image from a directory each time "random.jpg" was requested?

I know I could do something like that on the server, but I want to use it for message boards. I'm not trying to execute codes on the boards, merely instead of the server spitting out a 404 for random.jpg the php file handles it and supplies sig1.jpg or sign.jpg.

Also, I wouldn't mind use feed back on if people would be willing to put up with this (I've seen things where once a person does something, everyone picks up on it)
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Rysto
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Postby Rysto » Mon Sep 17, 2007 10:12 pm UTC

Yes, but it wouldn't work the way you wanted it to because of browser caches.

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Postby EvanED » Mon Sep 17, 2007 11:10 pm UTC

Rysto wrote:Yes, but it wouldn't work the way you wanted it to because of browser caches.

I haven't done anything in PHP for years, but I do know that you can send HTTP headers, which include things like cache-control to suppress caching on anyone who pays attention to the RFC.

My understanding is that, and IIRC, while you may need to use a couple headers to do the trick, you can accomplish that task most of the time.

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biolution
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Postby biolution » Tue Sep 18, 2007 3:09 am UTC

This is quite easy, really:

1) setup apache (or whatever webserver) to execute php when random.jpg is requested
2) randomly pick a file from your pile (however you do it is up to you)
3) (as others have mentioned) set http headers so clients don't cache the image. You can also append query params (?blalba) and fragments(#blabla) to help reduce this.

Additionally, you can simply keep the file name as "random.php" (<img src> doesn't care) so browsers don't try to guess the file type based on the name. Most likely you'll have to play around with it in IE to make sure it isn't caching it, since ie has a tendency to not give a shit what headers say.

This is probably gonna be useful.
http://www.google.com/search?q=how+to+p ... tp+caching

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Postby Karrion » Tue Sep 18, 2007 3:29 am UTC

You'll also need to make sure your php code sets the Content-Type header to the correct MIME type for the image file.

Basically you want to:
  1. Determine the available files and select one at random
  2. Set the Content-Type and Content-Length headers based on the selected file
  3. Set cache control headers
  4. Copy the image file from disk to output

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phlip
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Postby phlip » Tue Sep 18, 2007 3:59 am UTC

Another trick: if you set up Apache's content negotiation right (possibly also for other servers), you can call the script random.png.php and then access it as just random.png in the URL... or set up aliases to do a similar thing. That way it'll work for things like phpBB which expect an image-type filename extension.

If you don't have the ability to mess with the server settings, another way to do it is to make it random.png/index.php - then just access random.png... when you open it in the browser, the server will redirect you to random.png/ but that doesn't matter for when you put the URL into the "signature" box.

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enum ಠ_ಠ {°□°╰=1, °Д°╰, ಠ益ಠ╰};
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MrSomeone
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Postby MrSomeone » Tue Sep 18, 2007 10:09 pm UTC

What I did when I made a dynamic signature was had a directory dedicated to the signature, fir example /s/, and set the web server to process png files within that directory as PHP script (Apache: AddType application/x-httpd-php .png) then sig.png would actually be a PHP script outputting raw png data.

mod_rewrite can also be used, something like

Code: Select all

RewriteRule ^sig.png$ sig.php

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Jach
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Postby Jach » Wed Sep 19, 2007 1:48 am UTC

I did this several months ago. I just set up an Apache .htaccess to forward all 404 errors to the PHP file that grabs a random image and displays it.
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Postby Elevator_Hazard » Thu Sep 20, 2007 2:47 am UTC

I didn't really read up on this thread so much, but I made a random signature system already (currently doesn't work because the firewall on my host is trying to put ads in the image which produces errors) but I do have an image rotator. They both you .jpg files and you can see the imgRotator here. The .htaccess tells apache that .jpg files should be treated as .php files. The .htaccess code is here if you want to see it:

Code: Select all

<Files "img.jpg">

AddType application/x-httpd-php .jpg

</Files>
Image

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Durinthal
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Postby Durinthal » Thu Sep 20, 2007 3:21 am UTC

If people can do something like this:
Image

I'm sure just grabbing a random image isn't that hard.

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Re: Is this possible with PHP, a random signature?

Postby orygunbofh » Tue Oct 02, 2007 7:45 am UTC

I know your thread's getting a little old, but I've had some PHP + .htaccess goodness doing exactly this for a while now. Decided that it was time to dust it off, fix a bug or two, and publish it.

You can snag a tarball here, if you so desire. :)


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