Which image formats contain meta data, and how can I clear it in PHP?

[PhotoSHOPadob]

Privacy concerns have lead me to believe I should scrub user uploaded images for any meta data.I know that JPEG have EXIF, but I'm not sure about PNG or GIF (both are able to be uploaded to my site from the public).Do these formats have meta data too, and how is it stored? What is the best way to remove it?I'm using PHP 5.29.Thanks