random images

doobster

Hello,

I have a PHP script that will generate and display a random PNG image.

This part works great; however, the problem is the script always generates the same image each the page is loaded (image.png). When two people access the page at the same time the image.png is overwritted by the 2nd person who visits and the wrong image is displayed to the first person.

So far the only way I can think to over come this problem is to generate a random name for the image file. This is easy enough to do, but a space problem will then appear because I do not have permissions to run a CRON job and "clean up" the images every X minutes.

Does anyone know a good way around this to help me solve my problem?

sfullman

this is almost like a database issue.

Suggest you call session_start(); at the top of pages that use this.

then save your files as this:

$name[1]="img_".$PHPSESSID."_".1.".png";
//in case they need multiple images
$name[2]="img_".$PHPSESSID."_".2.".png";

Now, regarding the CRON job, I'd suggest no. Put all these images in a single folder, and assuming this feature that creates random images is the only feature that accesses this folder, then also have it manage deletions. i.e. every time an image is created, delete all images in the folder that are n minutes before the current time. Change n based on the usage level of the feature.

By the way do you write CRON? PM me with your email, I may need your help sometime!! :-)

HTH,
Sam Fullman
Compass Point Media

doobster

Thanks for the reply. Using the session id should work nicely.

But, how would I delete the files in the directory that are more than X minutes old.

As for the CRON, I don't write them as I stated I don't have access to CRON jobs on my server.

sfullman

you'd open the directory, and check the date on the file, hten compare the dates, see readdir in the php manual, or look at this code, once you get the file, read the timestamp, and then use unlink($file) if it is too old.

also, you'll need to chmod the folder sufficiently to be able to delete the file(s).

Sam

<?php
// Note that !== did not exist until 4.0.0-RC2

if ($handle = opendir('/path/to/files')) {
   echo "Directory handle: $handle\n";
   echo "Files:\n";

   /* This is the correct way to loop over the directory. */
   while (false !== ($file = readdir($handle))) { 
       echo "$file\n";
   }

   /* This is the WRONG way to loop over the directory. */
   while ($file = readdir($handle)) { 
       echo "$file\n";
   }

   closedir($handle); 
}
?>

doobster

Thanks for the help I got it all working now.