PHP Force Image Refresh
<img src="imagename.png?r=<?echo(rand());?>"> //produces a random number in url
Poised Penguin
<img src="imagename.png?r=<?echo(rand());?>"> //produces a random number in url//In PHP you can send a random number or the current timestamp
<img src="image.jpg?<?=Date('U')?>">
//or
<img src="image.jpg?<?=rand(1,32000)?>">