<?php
$password = "rasmuslerdorf";
$hash = password_hash($password, PASSWORD_BCRYPT, array("cost" => 7, "salt" => "usesomesillystringfor")));
if (password_verify($password, $hash)) {
    if (password_needs_rehash($hash, PASSWORD_BCRYPT, array('cost' => 8))) {
        update_password_in_db($password);
    }
    log_user_in();
} else {
    error_wrong_password();
}
?>