php教程

session_status

(PHP 5 >= 5.4.0, PHP 7)

session_status — 返回当前会话状态

说明

session_status ( void ) : int

session_status() 被用于返回当前会话状态。

返回值

  • PHP_SESSION_DISABLED 会话是被禁用的。
  • PHP_SESSION_NONE 会话是启用的，但不存在当前会话。
  • PHP_SESSION_ACTIVE 会话是启用的，而且存在当前会话。

参见

User Contributed Notes

info at eurocron dot de 06-Dec-2018 04:47
Use always session_status(), to check if a session is already started and active.
if(session_status() !== PHP_SESSION_ACTIVE) session_start();
or
if(session_status() === PHP_SESSION_NONE) session_start();

Don't use
if(!isset($_SESSION)) session_start();
or
if(session_id() === "") session_start();

They will not work properly after a call to session_write_close().
Both functions will continue to report, that the session exists.
And this is right, you can read from $_SESSION, but if you want to write,
you need session_start() again.

As a shorthand you can use
@session_start()
with the @ at the beginning to suppress the
PHP notice "A session had already been started - ignoring session_start()"

As stated in the manual for session_start(), a second call will do no harm,
it will be simply ignored. But you need the @, if you don't want to get the notice.
solaimanshah059 at gmail dot com 18-Aug-2018 09:10
Here some Good example for your understandingl

<?php

if( session_status == PHP_SESSION_NONE ) // if session status is none then start the session
{
     session_start();
}

?>

old Practice we were using.

<?php

if( !( isset($_SESSION) ) ) // if the session is no  set then start to
 new session
{
     session_start();
}

?>
ayon at hyurl dot com 09-Oct-2016 05:17
This is how the session_status() works:
<?php
function session_status(){
    if(!extension_loaded('session')){
        return 0;
    }elseif(!file_exists(session_save_path().'/sess_'.session_id()){
        return 1;
    }else{
        return 2;
    }
}
?>
Ben (aocool at msn d0t com) 16-Feb-2016 08:46
Just another function to determine whether the session has already started:

function is_session_started () {
    return function_exists ( 'session_status' ) ? ( PHP_SESSION_ACTIVE == session_status () ) : ( ! empty ( session_id () ) );
}
sasi dot viragelet at gmail dot co 01-Feb-2015 10:45
Maybe depending on PHP settings, but if return values are not the above, then go for this:
_DISABLED = 0
_NONE = 1
_ACTIVE = 2
Ollea 29-Jan-2014 11:02
If you started and closed a session then test ( session_id() === '' ) to check if a session is active it won't work, session_id() returns an ID even if the session is closed.

Anybody knows another way before PHP 5.4 to check if a session is really not currently active ?
coder dot ua at gmail dot com 15-Oct-2013 02:13
Universal function for checking session status.

<?php
/**
 * @return bool
 */
function is_session_started()
{
    if ( php_sapi_name() !== 'cli' ) {
        if ( version_compare(phpversion(), '5.4.0', '>=') ) {
            return session_status() === PHP_SESSION_ACTIVE ? TRUE : FALSE;
        } else {
            return session_id() === '' ? FALSE : TRUE;
        }
    }
    return FALSE;
}

// Example
if ( is_session_started() === FALSE ) session_start();
?>
php at kenman dot net 02-Aug-2013 03:45
The purpose of this functionality can aid you specifically in cases where code -- prior to your current code -- might have opened a session and then closed it.

Specifically, depending on $_SESSION, session_id(), and the SID constant to determine if a session is active will FAIL if a session has previously been opened & closed within the same request cycle.

Please see the original bug report here:

https://bugs.php.net/bug.php?id=52982
php at pointpro dot nl 16-Apr-2013 07:06
The advice of ive_insomnia at live dot com should be taken with great care.

First of all, while his use case for session_status is valid, a simpler way to avoid the warning is:

<?php
if (!isset($_SESSION)) { session_start(); }
?>

The example of session_status uses the raw values of constants (2 in this case) created specifically for the purpose of not having to use magic numbers.

Better code would be:

<?php
if (session_status() !== PHP_SESSION_ACTIVE) {session_start();}
?>

The same can be done using

<?
if (session_id() === "") { session_start(); }
?>

The use of this function is lies more towards status management: change the behavior of a script when sessions are disabled altogether, for example.

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