E-mail function not working correctly

[eluser]echo sara[/eluser]
no, the output of random_string defines it. its the scrambled letter/number.

Code:

function random_string() {
        $chars = "abcdefghijklmnopqrstuvwxyz0123456789";
        srand((double)microtime()*1000000);
        $i = 0;
        $pass = '';
        
        while ($i <= 7) {
            $num = rand() % 33;
            $tmp = substr($chars, $num, 1);
            $pass = $pass .$tmp;
            $i++;
        }
        
        return $activation_code;
    }