Bizarre (I think) session behaviour

[The Plankmeister]

Hi...

I'm using session_set_save_handler() and have defined some functions to
store session data in a database. It all works marvellously. Except for one
small thing. If I do something like:

...
if(isset($_SESSION['my_variable']))
...

the system calls the sess_write function, but passes an empty string as the
session variable parameter. Is this correct? I'm getting around this by
using an if clause and returning false if it's an empty string. This seems
to work ok. But is this correct behaviour? Or is it a bug?

TIA.

Plankmeister.

[CountScubula]

"The Plankmeister" <pl******************@hotmail.com> wrote in message news:<3f***********************@dread16.news.tele. dk>...

Hi...

I'm using session_set_save_handler() and have defined some functions to
store session data in a database. It all works marvellously. Except for one
small thing. If I do something like:

...
if(isset($_SESSION['my_variable']))
...

the system calls the sess_write function, but passes an empty string as the
session variable parameter. Is this correct? I'm getting around this by
using an if clause and returning false if it's an empty string. This seems
to work ok. But is this correct behaviour? Or is it a bug?

TIA.

Plankmeister.

This is correct behaviouir, you are checking to see if it isset,
basicaly a variable in use, it can contain nothing, example

isset($a) : false

$a = ""; // empty string, basicaly set to nothing, but set it is
isset($a) // evals to true

$a = array(); // empty array()
isset($a) // vals to tru

$a = ""; // empty string, basicaly set to nothing, but set it is
unset($a);// removes string from existance, off into nerver, never..
isset($a) // evals to false
change your if to this:
if( isset($_SESSION['my_variable'] != "" )
Mike Bradley
http://gzen.myhq.info -- free online php tools

[Agelmar]

CountScubula wrote:

"The Plankmeister" <pl******************@hotmail.com> wrote in
message news:<3f***********************@dread16.news.tele. dk>...

Hi...

I'm using session_set_save_handler() and have defined some functions
to
store session data in a database. It all works marvellously. Except
for one
small thing. If I do something like:

...
if(isset($_SESSION['my_variable']))
...

the system calls the sess_write function, but passes an empty string
as the
session variable parameter. Is this correct? I'm getting around this
by
using an if clause and returning false if it's an empty string. This
seems
to work ok. But is this correct behaviour? Or is it a bug?

TIA.

Plankmeister.

This is correct behaviouir, you are checking to see if it isset,
basicaly a variable in use, it can contain nothing, example

isset($a) : false

$a = ""; // empty string, basicaly set to nothing, but set it is
isset($a) // evals to true

$a = array(); // empty array()
isset($a) // vals to tru

$a = ""; // empty string, basicaly set to nothing, but set it is
unset($a);// removes string from existance, off into nerver, never..
isset($a) // evals to false
change your if to this:
if( isset($_SESSION['my_variable'] != "" )

Generally I would agree with Mike, except that the above code has two
problems. One, you're testing whether a boolean value is set
($_SESSION['something'] == 'something') will always evaluate to true or
false. This is pointless.

Secondly, to generalize, you want to know if something is empty, not equal
to the empty string. Therefore, for both semantic and readability reasons,
you should use empty().

empty($somevar) returns true if $somevar is
a) not defined (e.g. isset($somevar) == false)
b) equal to ""
c) equal to 0
d) equal to "0"
e) equal to NULL
f) equal to FALSE
g) equal to array()
h) equal to var $var (defined but not set to equal anything)
i) an object with empty properties.

[CountScubula]

> Secondly, to generalize, you want to know if something is empty, not equal

to the empty string. Therefore, for both semantic and readability reasons,
you should use empty().

Ah yes, I stand corrected. :)
Mike Bradley
http://gzen.myhq.info -- free online php tools