Most secure encryption in PHP

What is the most secure way to encrypt image data at rest in PHP? I have photos that need stored on the server short term (< 1 hour) which will then be unencrypted and viewed, and then destroyed with shred. If time isn’t a factor, meaning 10 seconds open time is ok, what’s the best encryption?

Edit: stop saying I’m doing something illegal; I work for law enforcement, assholes.