Posted by Marek Kilimajer on 04/11/05 23:32

Jochem Maas wrote:
> John Nichel wrote:
>
>> Jochem Maas wrote:
>>
>>> AndreaD wrote:
>>>
>>>> I have a session variable called
>>>>
>>>> $_SESSION['total'] the problem is I can't delete/reset it. I have tried
>>>>
>>>> $_SESSION['total']= 0;
>>>>
>>>> $_SESSION['total']= "";
>>>
>>>
>>>
>>>
>>> I guess you didn't know/think of trying null:
>>>
>>> $_SESSION['total'] = null;
>>>
>>> ...which has the same effect as using:
>>>
>>> unset($_SESSION['total']); // as you have been told on at least 3
>>> diff occasions ;-)
>>
>>
>>
>> Not true. If you set it to null, it still exists...it's just null.
>> If you unset it, the variable no longer exists.
>
>
> fair enough, but then how do you differentiate between a var that exists
> and is null
> and a non-existant var?
>
> Marek pointed out that setting error reporting to E_ALL, shows a notice
> when you var_dump() the unset() var and not the null var, but other than
> that
> the unset() var and the null var give the same result from isset() and
> empty()
> e.g:
>
> error_reporting(E_ALL);
> $X = array("total" => 1);
> $X["total"] = null;
> if ( isset ( $X["total"] ) ) {
> echo ( "Yes" );
> } else {
> echo ( "No" );
> }
> var_dump( $X["total"] );
> unset ( $X["total"] );
> if ( isset ( $X["total"] ) ) {
> echo ( "Yes" );
> } else {
> echo ( "No" );
> }
> var_dump( $X["total"] );
>
> which produces the following for me:
>
> NoNULL
> NoPHP Notice: Undefined index: total in Command line code on line 23
> NULL
>
> so that means you would have to set a suitable error handler for
> E_NOTICE just before
> the place you want to check if the var exists and unset it immediately
> afterwards??

No, use isset() or empty() to check if the variable exists and you won't
get notices

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