email - How to generate a secure activation string in php?

Question

After user subscribe email to my website. My website will generate an email confirmation and send to them. In the email content, i need to include activation key, something like:

www.domain.com/activate.php?key=$generatedKey

How do you generate the key? using sha1($email)??

After generate the key, i store it in database, so that when user click the link I can verified it with the database?? I am new to it, please advise.. I need an Email Confirmation script..

Answer 1

Personally, just I use a combination of things like:

$generatedKey = sha1(mt_rand(10000,99999).time().$email);

The chance of collision is small, but I recommend checking your database first before sending it out (using UNIQUE constraints is an easy way).