Image Cache Problem

Take me hours to googling around. Trying so many header suggestion, none of them work.

Here is my problem:
I have a page that upload picture.
After upload i display the new picture.
The picture name is the same before and after, ( rename the old one with new one ).
The picture on that page still referring to the old picture ....

The solution. Give the image src a random number .... (code it appropritely)

$randomnumber  = time();

<img src=myimage.jpg?$randomnumber >

This work immediatlly...