Posted by Jochem Maas on 04/12/05 00:21

Marek Kilimajer wrote:
> 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
>

right, I'm thinking about it too much - getting confused for no reason :-).
but that still leaves the point that you can't tell the difference between a
null var and one that is not set at all - this seems odd if there is actually
a difference (okay so you can tell the difference but it seems to require that
you generate an E_NOTICE which is not the idea really is it).

as I said I use empty(), isset() and null with out actually thinking about it...
they just do what I mean :-) which is great credit to the guys that wrote php
and hid all the intricacies of types/nulls etc from your average phper like me!

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