copy, open, or manipulate an image hosted in a https server

Hello, I need to copy, open or manipulate a gif images that is hosted in a https server. But when i try to do this, i recive a warning like this: *Warning*: imagecreatefromgif(https://..../aaa.gif): failed to open stream: Invalid argument in ..... I recive a similar message if i use: copy(https://..../aaa.gif,' bla bla bla '); fopen (https://..../aaa.gif, ....); How can i resolve this problem and use this image? Thanks, RB