Is it possible for the md5 hashes of two different strings to be the same?

[bluebeast]

title.

[markl999]

Yes

[cranial-bore]

yes, but very unlikely. If your concerned you could compare the md5 hash and an sha1 hash on the two strings.
The chance of BOTH being the same is unimaginably small.

[bluebeast]

I wasn't planning to use it for a log in system, I was going to use it for an image upload form, to name the image.

As long as everyones username is different, and no user can upload 2 images at the same time, I planned to md5 hash the username + time.

[spikeZ]

You should be fine then
If you are really REALLY paraniod that it might happen, use microtime() instead

[bluebeast]

Yes im very paranoid when it comes to these things, though I think I gotta better idea now username + timestamp, doesnt look like i will need to hash, as long as the server allowsup to 41 characters in file names.

[spikeZ]

you can have as many characters as you need, VARCHAR allows 255 maximum