It should be noted that these are a few specific graphics functions that the average php driven site will not have in use. However, if you use a php based photo/graphics gallery, you should be finding out if any of the three compromised functions are in use in the code you run and have your hosting company update php ASAP. Without having read the specifics, the exploits seem to be able to be triggered by the server recieving an image. This would be an upload or photo fecth to somewhere remote. I would think that turning off uploads and remote file requests would keep you out of trouble till php is patched.