也许我太晚了，但也许有人需要它。你可以通过urlencode和decode。例如：

$url = 'https://example.com/';
      $this->session->set_userdata('url',urlencode($url));

而当你想取url.you时可以这样做：

$myurl = urldecode($_SESSION['url']);
      echo $myurl;

对于unset，就简单的这样：

unset($_SESSION['url']);

没有必要非常聪明，Codeigniter已经非常聪明了;
就这样做：

<?php
/**
 * set session variable 'redirect'
 * with URL and query string
 */
$this->session->set_userdata ( 'redirect', current_url () . '?'. $this->input->server ( 'QUERY_STRING' ) );

/**
 * get session variable 'redirect'
 * with URL and query <string></string>
 * and redirect to user
 */
redirect ( $this->session->userdata ( 'redirect' ) );

/*
If URL is: 
http://localhost/development/ci-admin-with-template/index.php?test=pass&user=valid
User will Redirect on: 
http://localhost/development/ci-admin-with-template/index.php?test=pass&user=valid

If URL is: 
http://localhost/development/ci-admin-with-template/?test=pass&user=valid
User will Redirect on: 
http://localhost/development/ci-admin-with-template/index.php?test=pass&user=valid
*/
?>

如何将get变量存储到会话中。
就像这样：

$domain = current_url(); //http://alpha.scrollr.co/app
$this->session->set_userdata('tile'   , 'TITLE'); //stores the title
$this->session->set_userdata('credit' , 'CREDIT'); //stores the credit
$this->session->set_userdata('caption', 'CAPTION'); //stores the caption

然后您可以在之后UNSET它们。

$this->session->unset_userdata('tile');
$this->session->unset_userdata('credit');
$this->session->unset_userdata('caption');

如何将get变量存储到会话中？
就像这样：

$domain = current_url(); //http://alpha.scrollr.co/app
$this->session->set_userdata('tile'   , 'TITLE'); //stores the title
$this->session->set_userdata('credit' , 'CREDIT'); //stores the credit
$this->session->set_userdata('caption', 'CAPTION'); //stores the caption

然后您可以在之后UNSET它们。

$this->session->unset_userdata('tile');
$this->session->unset_userdata('credit');
$this->session->unset_userdata('caption');