If it cannot save the thumbnail then $phpThumb->RenderToFile($thumb) is failing. I assume it is to do with your mkdir not creating the full path. Perhaps it is just creating 1 folder per run. So if you have an image 3 folders deep it would take 3 refreshes to generate. Would you be able to confirm this?
To remove the second error (Warning mkdir), just put an @ in front of mkdir. I have now done this in the demo code above.
error messages
If it cannot save the thumbnail then $phpThumb->RenderToFile($thumb) is failing. I assume it is to do with your mkdir not creating the full path. Perhaps it is just creating 1 folder per run. So if you have an image 3 folders deep it would take 3 refreshes to generate. Would you be able to confirm this?
To remove the second error (Warning mkdir), just put an @ in front of mkdir. I have now done this in the demo code above.