What is the best way to create a short (6 chars), random, and with low collison probability? I need to create short links like bit.ly.
The problem of md5, sha1, uniqid etc. is that they don't generate uppercase characters, so I'm looking for a case-sensitive output to have a wider range of possible values...
I like to use Hashids for this kind of thing:
Hashids is a small open-source library that generates short, unique, non-sequential ids from numbers.
It converts numbers like 347 into strings like “yr8”, or array of numbers like [27, 986] into “3kTMd”.
You can also decode those ids back. This is useful in bundling several parameters into one or simply using them as short UIDs.
Hashids has been ported to many languages, including PHP.
(Note that, despite the name, Hashids is not a true hashing system since it is designed to be reversible.)