; Argument passed to save_handler.  In the case of files, this is the path
; where data files are stored. Note: Windows users have to change this
; variable in order to use PHP's session functions.
;
; As of PHP 4.0.1, you can define the path as:
;
;     session.save_path = "N;/path"
;
; where N is an integer.  Instead of storing all the session files in
; /path, what this will do is use subdirectories N-levels deep, and
; store the session data in those directories.  This is useful if you
; or your OS have problems with lots of files in one directory, and is
; a more efficient layout for servers that handle lots of sessions.
;
; NOTE 1: PHP will not create this directory structure automatically.
;         You can use the script in the ext/session dir for that purpose.
; NOTE 2: See the section on garbage collection below if you choose to
;         use subdirectories for session storage
;
; The file storage module creates files using mode 600 by default.
; You can change that by using
;
session.save_path = "2;666;/var/sessions/php"

; Define how many bits are stored in each character when converting
; the binary hash data to something readable.
;
; 4 bits: 0-9, a-f
; 5 bits: 0-9, a-v
; 6 bits: 0-9, a-z, A-Z, "-", ","
session.hash_bits_per_character = 5

try {
    Zend_Session::start();
} catch (Exception $e) {
    // echo $e->getMessage(); -> Zend_Session::start() - session_start() [function.session-start]: open(/var/sessions/php/x/x/sess_xxx, O_RDWR) failed: No such file or directory (2)
    Zend_Session::regenerateId();
    // echo session_id(); // -> xxx
    Zend_Session::setId('test'); -> Exception: The session has already been started. The session id must be set first.
}

$hashBitsPerChar = ini_get('session.hash_bits_per_character');
if (!$hashBitsPerChar) {
    $hashBitsPerChar = 5; // the default value
}
switch($hashBitsPerChar) {
    case 4: $pattern = '^[0-9a-f]*$'; break;
    case 5: $pattern = '^[0-9a-v]*$'; break;
    case 6: $pattern = '^[0-9a-zA-Z-,]*$'; break;
}
if ( !preg_match('#'.$pattern.'#', session_id()) ) {
    throw new Zend_Session_Exception('Invalid session id "'.session_id.'"');
}