Welcome back, GIF!
Only a couple of days are left until the patent on the, mostly used in GIF and TIF images, LZW compression algorithm runs out. The patent, hold by Unisys has already expired in the USA last year. Today it expires in Europe, too, and Canada (as the last state worldwide) will follow on July the 7th.
GIF support has been disabled some years ago in most of the open source software and so in PHP, since Unisys made demands on high license fees for their patent on the optimized LZW algorithm. Only some open source products had GIF support, but mostly with any kind of compression, which made the file format in some way inattractive. PNG (Portable Network Graphics) should have become the successor of GIF in those times, but has never really managed to become equally popular.
Now, that the LZW patent has nearly expired all over the world, GIF support may return into open source (and also closed) software without license fees, which will give the old format (which was introduced by Compuserve in 1987) a come-back. And this, although PNG has much more features (like gradient transparency).
Rumors are spreading, that support for GIF creation will return into PHP's bundled GD library again for the release 4.3.8, since this is an old, deactivated, features and not a new one, which would fall under the "feature freeze" for PHP 4. Hopefully it will be part of the next PHP5 release.
So: Welcome back, GIF!