PHP: How to generate a random, unique, alphanumeric string for use in a secret link?

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 y

Answer 1

When trying to generate a random password you are trying to :

• First generate a cryptographically secure set of random bytes

• Second is turning those random bytes into a printable string

Now, there are multiple way to generate random bytes in php like :

$length = 32;

//PHP 7+
$bytes= random_bytes($length);

//PHP < 7
$bytes= openssl_random_pseudo_bytes($length);

Then you want to turn these random bytes into a printable string :

You can use bin2hex :

$string = bin2hex($bytes);

or base64_encode :

$string = base64_encode($bytes);

However, note that you do not control the length of the string if you use base64. You can use bin2hex to do that, using 32 bytes will turn into a 64 char string. But it will only work like so in an EVEN string.

So basically you can just do :

$length = 32;

if(PHP_VERSION>=7){
    $bytes= random_bytes($length);
}else{
    $bytes= openssl_random_pseudo_bytes($length);
} 

$string = bin2hex($bytes);