PHP: How to generate a random, unique, alphanumeric string?

Question

How would it be possible to generate a random, unique string using numbers and letters for use in a verify link? Like when you create an account on a website, and it sends you an email with a link, and you have to click that link in order to verify your account...yeah...one of those.

How can I generate one of those using PHP?

Update: Just remembered about uniqid(). It's a PHP function that generates a unique identifier based on the current time in microseconds. I think I'll use that.

Answer 1

Try this: Random MD5 Strings

Answer 2

1. Generate a random number using your favourite random-number generator
2. Multiply and divide it to get a number matching the number of characters in your code alphabet
3. Get the item at that index in your code alphabet.
4. Repeat from 1) until you have the length you want

e.g (in pseudo code)

int myInt = random(0, numcharacters)
char[] codealphabet = 'ABCDEF12345'
char random = codealphabet[i]
repeat until long enough

Answer 3

If you do not need it to be absolutely unique over time:

md5(uniqid(rand(), true))

Otherwise (given you have already determined a unique login for your user):

md5(uniqid($your_user_login, true))

Answer 4

Here's one that seems to work - http://kevin.vanzonneveld.net/techblog/article/create_short_ids_with_php_like_youtube_or_tinyurl/