While registering with a website we often need to verfy our email id. Given below is the code to develop that functionality. The following will generate the verification key which has 6 characters
function generatePassword()
{
$length =6;
$validchars = "0123456789abcdfghjkmnpqrstvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
$password ="";
$counter = 0;
while($counter < $length)
{
$actChar = substr($validchars, rand(0, strlen($validchars)), 1);
if(!strstr($password, $actchar))
{
$password .= $actChar;
$counter++;
}
}
return $password;
}
rand(0, stlen($validchars)) – generates a random number between 0 and the length of $validchars (inclusive of both ends).
substr($a, $b , len) – get generates a sub string from $a from the first occurrence of $b to length specified by len.
strstr($a, $b) – checks whether $a has $b in it. This is done to create unique characters.
So this is how you generate random string. How you can use it for verification purpose of a user registration is explained in the subsequent posts.

What programming language is this, PHP? I was about to write a couple of ways to make it more Perlish, before I realized it wasn’t Perl!
BTW, your check to avoid duplicated chars actually reduces the randomness of these verification keys.