ImageGif newbie question

I am trying to write a gif image to a file...when I use ImageGif, I am
able to view the newly generated file just fine...but when I try this:

$filegif = fopen("images/myfile.gif", "w"); 
ImageGif($im, "images/myfile.gif");
fclose($filegif);                                              

I get a permission denied message...to give some background, the
myfile.gif does not exist, so the "w" should create it, so I have read.
The question I have is, since this is a permissions issue, do I have to
change the permissions on the images directory, in order to write to it?
I don't want to have to give write permissions to the world, and since
this is server side, I didn't think I had to...anyone have a clue about
this?

Thanks in Advance,
Jessica