session.php 14.6 KB
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<?php
/**
 *
 * @package    mahara
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 * @subpackage core
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 * @author     Catalyst IT Ltd
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 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL version 3 or later
 * @copyright  For copyright information on Mahara, please see the README file distributed with this software.
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 *
 */

defined('INTERNAL') || die();

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//
// Set session settings
//
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session_name(get_config('cookieprefix') . 'mahara');
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$sessionpath = get_config('sessionpath');
ini_set('session.save_path', '3;' . $sessionpath);
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ini_set('session.gc_divisor', 1000);
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ini_set('session.gc_maxlifetime', get_config('session_timeout'));
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ini_set('session.use_only_cookies', true);
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if ($domain = get_config('cookiedomain')) {
    ini_set('session.cookie_domain', $domain);
}
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ini_set('session.cookie_path', get_mahara_install_subdirectory());
ini_set('session.cookie_httponly', 1);
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ini_set('session.hash_bits_per_character', 4);
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ini_set('session.hash_function', 0);
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if (is_https()) {
    ini_set('session.cookie_secure', true);
}
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// Attempt to create session directories
if (!is_dir("$sessionpath/0")) {
    // Create three levels of directories, named 0-9, a-f
    $characters = array('0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f');
    foreach ($characters as $c1) {
        check_dir_exists("$sessionpath/$c1");
        foreach ($characters as $c2) {
            check_dir_exists("$sessionpath/$c1/$c2");
            foreach ($characters as $c3) {
                check_dir_exists("$sessionpath/$c1/$c2/$c3");
            }
        }
    }
}

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/**
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 * The session class handles session data and messages.
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 *
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 * This class stores information across page loads, using only a cookie to
 * remember the info. User information is stored in the session so it does
 * not have to be requested each time the page is loaded, however any other
 * information can also be stored using this class.
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 *
 * This class also is smart about giving out sessions - if a visitor
 * has not logged in (e.g. they are a guest, searchbot or a simple
 * 'curl' request), a session will not be created for them.
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 *
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 * Messages are stored in the session and are displayed the next time
 * a page is displayed to a user, even over multiple requests.
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 *
 * In addition, to allow the json progress meter to do its work, this
 * class maintains the session state, keeping it read-only except as
 * necessary (in order to not block the progress meter json calls).
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 */
class Session {

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    /**
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     * Resumes an existing session, only if there is one
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     */
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    private function __construct() {
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        // Resume an existing session if required
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        if (isset($_COOKIE[session_name()])) {
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            @session_start();
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            // But it's not writable except through functions below.
            $this->ro_session();
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        }
    }

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    /**
     * Singelton function keeps us from generating multiple instances of this
     * class
     *
     * @return object   The class instance
     * @access public
     */
    public static function singleton() {
        //single instance
        static $instance;

        //if we don't have the single instance, create one
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        if (!isset($instance)) {
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            $instance = new Session();
        }
        return($instance);
    }

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    /**
     * Gets the session property keyed by $key.
     *
     * @param string $key The key to get the value of
     * @return mixed
     */
    public function __get($key) {
        return $this->get($key);
    }

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    /**
     * Gets the session property keyed by $key.
     *
     * @param string $key The key to get the value of
     * @return mixed
     */
    public function get($key) {
        if (isset($_SESSION[$key])) {
            return $_SESSION[$key];
        }
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        return null;
    }

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    /**
     * Sets the session property keyed by $key.
     *
     * @param string $key The key to get the value of
     * @return mixed
     */
    public function __set($key, $value) {
        return $this->set($key, $value);
    }

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    /**
     * Sets the session property keyed by $key.
     *
     * @param string $key   The key to set.
     * @param string $value The value to set for the key
     */
    public function set($key, $value) {
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        $this->ensure_session();
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        if (is_null($value)) {
            unset($_SESSION[$key]);
        }
        else {
            $_SESSION[$key] = $value;
        }
        $this->ro_session();
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    }

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    /**
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     * Unsets the session property keyed by $key.
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     *
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     * @param string $key   The key to remove.
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     */
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    public function __unset($key) {
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        $this->ensure_session();
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        unset($_SESSION[$key]);
        $this->ro_session();
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    }

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    /**
     * Old way of clearing session property - added for backwards compatibility
     *
     * @param string $key   The key to remove.
     */
    public function clear($key) {
        $this->__unset($key);
    }

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    /**
     * Adds a message that indicates something was successful
     *
     * @param string $message The message to add
     * @param boolean $escape Whether to HTML escape the message
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     * @param string $placement Place for messages to appear on page (See render_messages()
     *     for information about placement options)
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     */
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    public function add_ok_msg($message, $escape=true, $placement='messages') {
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        $this->ensure_session();
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        if ($escape) {
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            $message = self::escape_message($message);
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        }
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        $_SESSION['messages'][] = array('type' => 'ok', 'msg' => $message, 'placement' => $placement);
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        $this->ro_session();
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    }

    /**
     * Adds a message that indicates an informational message
     *
     * @param string $message The message to add
     * @param boolean $escape Whether to HTML escape the message
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     * @param string $placement Place for messages to appear on page (See render_messages()
     *     for information about placement options)
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     */
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    public function add_info_msg($message, $escape=true, $placement='messages') {
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        $this->ensure_session();
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        if ($escape) {
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            $message = self::escape_message($message);
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        }
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        $_SESSION['messages'][] = array('type' => 'info', 'msg' => $message, 'placement' => $placement);
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        $this->ro_session();
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    }

    /**
     * Adds a message that indicates a failure to do something
     *
     * @param string $message The message to add
     * @param boolean $escape Whether to HTML escape the message
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     * @param string $placement Place for messages to appear on page (See render_messages()
     *     for information about placement options)
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     */
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    public function add_error_msg($message, $escape=true, $placement='messages') {
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        $this->ensure_session();
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        if ($escape) {
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            $message = self::escape_message($message);
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        }
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        $_SESSION['messages'][] = array('type' => 'error', 'msg' => $message, 'placement' => $placement);
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        $this->ro_session();
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    }

    /**
     * Builds HTML that represents all of the messages and returns it.
     *
     * This is designed to let smarty templates hook in any session messages.
     *
     * Calling this function will destroy the session messages that were
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     * assigned to the $placement, so they do not inadvertently get
     * displayed again.
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     *
     * To define where the messages for a particular $placement value should be displayed,
     * add this code to a page template:
     *
     *   {dynamic}{insert_messages placement='your_placement_name_here'}{/dynamic}
     *
     * The default 'messages' placement is shown on every page, and is suitable for most purposes.
     * Alternative placements should only be needed in special situations, such as showing a login-related
     * error in the login box. Note that messages will hang around in the $SESSION until a page template
     * with their "placement" in it is loaded. So, they should only be used in situations where you're
     * certain their placement zone will be present on the next page load, or else the user may be
     * confused by their appearance several page loads later.
     *
     * @param string $placement Render only messages for this placement
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     *
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     * @return string The HTML representing all of the session messages assigned
     * to $placement.
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     */
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    public function render_messages($placement = 'messages') {
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        global $THEME;
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        $result = '<div id="' . $placement . '" role="alert" aria-live="assertive">';
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        if (isset($_SESSION['messages'])) {
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            $this->ensure_session();  // Make it writable and lock against other threads.
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            foreach ($_SESSION['messages'] as $key => $data) {
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                $typeClass = $data['type'] === 'ok' ? 'success' : $data['type'];

                if ($typeClass === 'error') {
                    $typeClass = 'danger';
                }

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                if ($data['placement'] == $placement) {
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                    $result .= '<div class="alert alert-' . $typeClass . '"><div>';
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                    $result .= $data['msg'] . '</div></div>';
                    unset($_SESSION['messages'][$key]);
                }
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            }
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            $this->ro_session();
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        }
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        $result .= '</div>';
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        return $result;
    }

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    public function set_progress($token, $content) {
        // Make the session writable.
        $this->ensure_session();

        if ($content === FALSE) {
            unset($_SESSION['progress_meters'][$token]);
        }
        else {
            $_SESSION['progress_meters'][$token] = $content;
        }

        // Release our lock.
        $this->ro_session();
    }

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    /**
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     * Create a session, by initialising the $_SESSION array.
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     */
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    private function ensure_session() {
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        if (defined('CLI')) {
            return;
        }

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        if (empty($_SESSION)) {
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            @session_start();
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            $_SESSION = array(
                'messages' => array()
            );
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        }
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        else {
            @session_start();
        }
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        // Anytime you call session_start() more than once, PHP will usually
        // send out a duplicate session header.
        clear_duplicate_cookies();
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    }

    /*
     * Make a session readonly after modifying it.
     *
     * The session must have been opened already.
     */

    private function ro_session() {
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        if (defined('CLI')) {
            return;
        }

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        session_write_close();
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    }

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    /**
     * Destroy a session
     */
    public function destroy_session() {
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        if (defined('CLI')) {
            return;
        }

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        if ($this->is_live()) {
            $_SESSION = array();
            if (isset($_COOKIE[session_name()])) {
                setcookie(session_name(), '', time() - 65536,
                    ini_get('session.cookie_path'),
                    ini_get('session.cookie_domain'),
                    ini_get('session.cookie_secure'),
                    ini_get('session.cookie_httponly')
                );
            }
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            @session_start();
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            session_destroy();
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            clear_duplicate_cookies();
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        }
    }

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    /**
     * Find out if the session has been started yet
     */
    public function is_live() {
        if ("" == session_id()) {
            return false;
        }
        return true;
    }

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    /**
     * Escape a message for HTML output
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     *
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     * @param string $message The message to escape
     * @return string         The message, escaped for output as HTML
     */
    private static function escape_message($message) {
        $message = hsc($message);
        $message = str_replace('  ', '&nbsp; ', $message);
        return $message;
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    }
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}

/**
 * A smarty callback to insert page messages
 *
 * @return string The HTML represening all of the session messages.
 */
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function insert_messages($placement='messages') {
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    global $SESSION;
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    return $SESSION->render_messages($placement);
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}

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/**
 * Delete all sessions belonging to a given user except for the current one
 */
function remove_user_sessions($userid) {
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    global $sessionpath, $USER, $SESSION;
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    $sessionids = get_column('usr_session', 'session', 'usr', (int) $userid);
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    if (empty($sessionids)) {
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        return;
    }

    $alive = array();
    $dead = array();
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    // Keep track of the current session id so we can return to it at the end
    if ($SESSION->is_live()) {
        $sid = $USER->get('sessionid');
    }
    else {
        // The user has no session (this function is being called by a CLI script)
        $sid = false;
    }

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    foreach ($sessionids as $sessionid) {
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        if ($sessionid == $sid) {
            continue;
        }
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        $file = $sessionpath;
        for ($i = 0; $i < 3; $i++) {
            $file .= '/' . substr($sessionid, $i, 1);
        }
        $file .= '/sess_' . $sessionid;
        if (file_exists($file)) {
            $alive[] = $sessionid;
        }
        else {
            $dead[] = $sessionid;
        }
    }

    if (!empty($dead)) {
        delete_records_select('usr_session', 'session IN (' . join(',', array_map('db_quote', $dead)) . ')');
    }

    if (empty($alive)) {
        return;
    }

    session_commit();

    foreach ($alive as $sessionid) {
        session_id($sessionid);
        if (session_start()) {
            session_destroy();
            session_commit();
        }
    }

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    if ($sid !== false) {
        session_id($sid);
        session_start();
    }
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    clear_duplicate_cookies();
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    delete_records_select('usr_session', 'session IN (' . join(',', array_map('db_quote', $alive)) . ')');
}

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/**
 * Delete all session files except for the current one
 */
function remove_all_sessions() {
    global $sessionpath, $USER;

    $sid = $USER->get('sessionid');

    $iterator = new RecursiveIteratorIterator(new RecursiveDirectoryIterator($sessionpath));
    foreach ($iterator as $path) {
        if ($path->isFile() && $path->getFilename() !== ('sess_' . $sid)) {
            @unlink($path->getPathname());
        }
    }
    clearstatcache();

    delete_records_select('usr_session', 'session != ?', array($sid));
}
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/**
 * Every time you call session_start(), PHP adds another
 * identical session cookie to the response header. Do this
 * enough times, and your response header becomes big enough
 * to choke the web server.
 *
 * This method clears out the duplicate session cookies.
 */
function clear_duplicate_cookies() {
    // If headers have already been sent, there's nothing we can do
    if (headers_sent()) {
        return;
    }

    $cookies = array();
    foreach (headers_list() as $header) {
        // Identify cookie headers
        if (strpos($header, 'Set-Cookie:') === 0) {
            $cookies[] = $header;
        }
    }
    // Removes all cookie headers, not just the session one.
    header_remove('Set-Cookie');

    // Restore one copy of each cookie
    foreach(array_unique($cookies) as $cookie) {
        header($cookie, false);
    }
}