How do check if a PHP session is empty?

Question

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

score 112 · Accepted Answer · edited Dec 31 '17 at 07:25

112

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.

edited Dec 31 '17 at 07:25

Shiv Singh

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answered Oct 05 '09 at 12:41

karim79

339,989
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9

no need to use isset if you are already using empty. empty will also check if the variable exists, i.e. is not null/undefined – knittl Oct 05 '09 at 12:47
1

No need to use isset AND empty. – Patrick Desjardins Oct 05 '09 at 12:49
6

@knittl It's good practice to actually make sure you have the variable before testing to see if it's empty. – random Oct 05 '09 at 12:49
2

@knittl - but then we don't know if it's been set or not, whether it's not set *or* empty true will be returned. I tend to use the above, but it might not always be needed. – karim79 Oct 05 '09 at 12:50
4

Empty return false when not exist or null or "" or empty array. Why would you need to check if isset too? Read the help file : http://ca.php.net/empty – Patrick Desjardins Oct 05 '09 at 12:52
2

@Daok Variables can both exist and be blank. Checking to see if it exists AND is empty is a good idea. – random Oct 05 '09 at 12:52
usually you either want to check if the variable exists (`isset`) or if it contains any value evaluating to false (0, "0", null, false, …) (`empty`). `empty` will also return true on unset variables, so you don’t need `isset` first – knittl Oct 05 '09 at 12:54
3

@random it is __not__ good practice! Its just redundant. See http://stackoverflow.com/questions/4559925/why-check-both-isset-and-empty – Adam Mar 24 '17 at 11:26
The issue I have is when I do form submission it shows the session isn't empty but doesn't pull value for the session for some reason. Any idea why that may happen. – Si8 Apr 19 '18 at 16:05
So I have to use `isset` or checking `empty` is sufficient enough? – Si8 Apr 19 '18 at 16:15
oh wow, on my logout page, I forgot to call the session_start(); at the top of the page, otherwise it would run without any errors, and without actually unsetting the session variables. – hamish Jul 15 '19 at 16:37
@PatrickDesjardins If you do not check empty it will try to do some strange things like: Array to string conversion in It tries to take your empty session log and convert to an array..... – Yunfei Chen Oct 09 '20 at 23:53

score 12 · Answer 2 · answered Oct 05 '09 at 12:46

12

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'] == '')

answered Oct 05 '09 at 12:46

Gumbo

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844

score 6 · Answer 3 · answered Oct 05 '09 at 12:40

6

you are looking for PHP’s empty() function

answered Oct 05 '09 at 12:40

knittl

246,190
53
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20

empty is dangerous because it also reports false, 0 and "0" as empty. – OIS Oct 05 '09 at 12:51

score 4 · Answer 4 · answered Oct 05 '09 at 12:41

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)

score 4 · Answer 5 · answered Oct 05 '09 at 12:49

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).

score 0 · Answer 6 · answered Feb 27 '14 at 19:36

0

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

answered Feb 27 '14 at 19:36

hfarazm

1,407
17
22

score 0 · Answer 7 · answered May 30 '19 at 21:50

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');
         }

How do check if a PHP session is empty?

7 Answers7

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