Migrate new user accounts from Drupal 6 site to Drupal 7 site. Run this in devel php. Source: stackoverflow

migrate_user_d2d.php

<?php

require_once "./includes/password.inc";

//connect to Drupal 6 database
//syntax:mysqli(hostname,username,password,databasename);
$db= new mysqli('localhost','root','rootpwd','db');
if(mysqli_connect_errno())  {
    echo "Conection error. Could not connect to Drupal 6 site!";
    exit;
}

//get users from Drupal 6 database
$query="select * from users";
$result=$db->query($query);
//count number of users
$num_results=$result->num_rows;
for($i=0;$i<$num_results;$i++){

    //fetch each row/user
    $row=$result->fetch_assoc();

    //migrate only active users
    if($row['status']==1){

        //convert password from Drupal 6 style to Drupal 7 style
        $hashed_pass='U'.user_hash_password($row['pass'],11);

        //check if user with same email address already exists in Drupal 7 database, if it does, do not migrate
        if (!user_load_by_mail($row['mail'])) {
            $account = new stdClass;
            $account->is_new = TRUE;
            $account->name = $row['name'];
            $account->pass = $hashed_pass;
            $account->mail = $row['mail'];
            $account->init = $row['mail'];
            $account->status = TRUE;
            $account->roles = array(DRUPAL_AUTHENTICATED_RID => TRUE);
            $account->timezone = variable_get('date_default_timezone', '');
            //create user in Drupal 7 site 
            user_save($account);
            //print message
            echo "User acount ".$row['name']." has been created\n";
        }
    }

}

?>