Create Unique Image Names

Question

What\'s a good way to create a unique name for an image that my user is uploading?

I don\'t want to have any duplicates so something like MD5($filename) isn\'t suita

Answer 1

Grab the file extension from uploaded file:

$ext = pathinfo($uploaded_filename, PATHINFO_EXTENSION);

Grab the time to the second: time()

Grab some randomness: md5(microtime())

Convert time to base 36: base_convert (time(), 10, 36) - base 36 compresses a 10 byte string down to about 6 bytes to allow for more of the random string to be used

Send the whole lot out as a 16 char string:

$unique_id = substr( base_convert( time(), 10, 36 ) . md5( microtime() ), 0, 16 ) . $ext;

I doubt that will ever collide - you could even not truncate it if you don't mind very long file names.