如何检查PHP会话是否为空？

Is this bad practice?

if ($_SESSION['something'] == '')
{
    echo 'the session is empty';
}

Is there a way to check if its empty or it is not set? I'm actualy doing this:

if (($_SESSION['something'] == '') || (!isset($_SESSION['something'])) {
    echo 'the session is either empty or doesn\'t exist';
}

Does !isset just checks if a $_SESSION[''] exist and doesn't check if, is there are values in the array or not

I would use isset and empty:

session_start();
if(isset($_SESSION['blah']) && !empty($_SESSION['blah'])) {
   echo 'Set and not empty, and no undefined index error!';
}

array_key_exists is a nice alternative to using isset to check for keys:

session_start();
if(array_key_exists('blah',$_SESSION) && !empty($_SESSION['blah'])) {
    echo 'Set and not empty, and no undefined index error!';
}

Make sure you're calling session_start before reading from or writing to the session array.

you are looking for PHP’s empty() function

You could use the count() function to see how many entries there are in the $_SESSION array. This is not good practice. You should instead set the id of the user (or something similar) to check wheter the session was initialised or not.

if( !isset($_SESSION['uid']) )
    die( "Login required." );

(Assuming you want to check if someone is logged in)

Use isset, empty or array_key_exists (especially for array keys) before accessing a variable whose existence you are not sure of. So change the order in your second example:

if (!isset($_SESSION['something']) || $_SESSION['something'] == '')

If you want to check whether sessions are available, you probably want to use the session_id() function:

session_id() returns the session id for the current session or the empty string ("") if there is no current session (no current session id exists).

if(isset($_SESSION))
{}
else
{}

The best practice is to check if the array key exists using the built-in array_key_exists function.

I know this is old, but I ran into an issue where I was running a function after checking if there was a session. It would throw an error everytime I tried loading the page after logging out, still worked just logged an error page. Make sure you use exit(); if you are running into the same problem.

     function sessionexists(){
        if(!empty($_SESSION)){
     return true;
         }else{
     return false;
         }
      }


        if (!sessionexists()){
           redirect("https://www.yoursite.com/");
           exit();
           }else{call_user_func('check_the_page');
         }