php photo galery

Hello, I've googled for this and tried some downloads but not finding what i'm looking for. A site requirement is to have a photo gallery. These user's are not very technical so i thought about getting a galery with the ability to upload photos via a browser, I would also like thumb nails, and the ability to have an alt text attribute with the photo and a longer description of the picture, for accessibility reasons. If anyone has anything similar to this please let me know. Thanks. Dave.