getting a unique name for an uploaded file

Gladiator2043

i have a folder on the server that I am allowing users to upload image files......I am trying to develop a mechanism so that every uploaded file is unique.

any ideas?

cbj4074

Generate a random string of text (or numbers) of substantial length and then make an MD5 hash of that string, and use that for the file name? There are countless ways to do it...

Make sure the file name length and such conform to the requirements of your OS.

laserlight

You can use [man]uniqid/man in conjunction with say [man]sha1/man.

For example:

$identifier = sha1(uniqid(mt_rand(), true));

In you are really worried about repeating identifiers, then do a search first, and generate a new one if there is a match.

Gladiator2043

most excellent.

thankyou both!

Gladiator2043

i have 3 random values being output with this code:
which one is the best and safest to generate a unique file name???

$token = md5(uniqid(rand(),1));
echo $token;
?>

<BR>

<?PHP
//set the random id length
$random_id_length = 10;

//generate a random id encrypt it and store it in $rnd_id
$rnd_id = crypt(uniqid(rand(),1));

//to remove any slashes that might have come
$rnd_id = strip_tags(stripslashes($rnd_id));

//Removing any . or / and reversing the string
$rnd_id = str_replace(".","",$rnd_id);
$rnd_id = strrev(str_replace("/","",$rnd_id));

//finally I take the first 10 characters from the $rnd_id
$rnd_id = substr($rnd_id,0,$random_id_length);

echo "Random Id: $rnd_id";
?>

<BR>
<?
$identifier = sha1(uniqid(mt_rand(), true));
echo $identifier;