Bizarre (I think) session behaviour

[The Plankmeister]

Hi...

I'm using session_set_sav e_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($_SESS ION['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]

Re: Bizarre (I think) session behaviour

"The Plankmeister" <plankmeister_N OSPAM_@hotmail. com> wrote in message news:<3fee0949$ 0$27450$edfadb0 f@dread16.news. tele.dk>...[color=blue]
> Hi...
>
> I'm using session_set_sav e_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($_SESS ION['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.[/color]


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]

Re: Bizarre (I think) session behaviour

CountScubula wrote:[color=blue]
> "The Plankmeister" <plankmeister_N OSPAM_@hotmail. com> wrote in
> message news:<3fee0949$ 0$27450$edfadb0 f@dread16.news. tele.dk>...[color=green]
>> Hi...
>>
>> I'm using session_set_sav e_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($_SESS ION['my_variable']))
>> ...
>>
>> the system calls the sess_write function, but passes an empty string
>> as the
>> session variable parameter. Is this correct? I'm getting around this
>> by
>> using an if clause and returning false if it's an empty string. This
>> seems
>> to work ok. But is this correct behaviour? Or is it a bug?
>>
>> TIA.
>>
>> Plankmeister.[/color]
>
>
> This is correct behaviouir, you are checking to see if it isset,
> basicaly a variable in use, it can contain nothing, example
>
> isset($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'] != "" )[/color]

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]

Re: Bizarre (I think) session behaviour

> Secondly, to generalize, you want to know if something is empty, not equal[color=blue]
> to the empty string. Therefore, for both semantic and readability reasons,
> you should use empty().
>[/color]

Ah yes, I stand corrected. :)


Mike Bradley
http://gzen.myhq.info -- free online php tools