Browser keep the image when the source is changed

Hi, I have a strange problem!
I put an img in the browser say <img src='abc.png'>.
When I change the image (keep the same name) and then refresh the window. The browser displayed the original image. How to let the browser display the new image?

How to let the browser display the new image?
It's due to the caching of files by the browser. You may solve this by a hard refresh (Ctrl+F5). Or simple add different numbers or string at the end of file name, like
<img src='abc.png?1'>
<img src='abc.png?2'>

Thank you very much, this works pretty well! use let $_SESSION['logo_tail'] add 1 every the time the user refresh the window.