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Date: Wed, 03 Nov 2004 19:35:14 +0100
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To: Andrey Hristov <php@hristov.com>
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Subject: Re: [PHP-DEV] serialize bug with array that references to itself?
From: jochem@iamjochem.com (Jochem Maas)

Hi Andrey,

I have to confess my understanding of the engine internals is next to 
zero, but I do understand that var_dump and print_r were created 
with/for different pretexts.

I agree with you that printing nothing for NULL is doesn't feel right 
(btw boolean false has the same effect) - this can be problematic when 
you don't know that this is the case (indeed much time have I lost on 
this issue when I first started out), this is a minor gripe and easily 
sidestepped with a var_dump :-)

my question was more out of curiosity (although I would like to see the 
threshold for var_dump dropped to 2 if that is technically 
feasible/acceptable) - there may be a good reason for the difference in 
thresholds, it may be a an oversight/inconsistency. either way my motive 
is to better understand the reasoning behind the way things work in PHP 
- better understanding how/why a developer made it work a certain has in 
the past really helped me improve my code.

thanking everyone who has made (and continues to make) PHP what it is - 
it rocks alot more than it doesn't ;-).

Andrey Hristov wrote:
>  Hi,
> print_r() and var_dump() are quite different in their nature.
> print_r() is a thin wrapper around an internal Zend function
> (as far as I remember) while var_dump() is in ext/standard/var.c
> The do more or less the same job still some differences in the
> output (print_r() shows nothing on NULL variables which I find
> clumsy since lack of output where I expect ouput makes me
> suspicious).
> 
> Andrey
> 
> Jochem Maas wrote:
> 
>> Andrey Hristov wrote:
>>
>>>  Well, when there is traversion inside the engine, it checks whether 
>>> it has
>>> processed a "node" already several times. As far as I remember the 
>>> threshold
>>> is 3. So once it goes over $Arr, the counter increases to 1, the 
>>> second time
>>> to 2 and third time it is 3 and ZE reports recursion.
>>
>>
>>
>> is there good reason to set the threshold at 3 iso 2?
>>
>> when dumping out objects that make heavy use of 'parent' references 
>> this leads to tons of extra output which would be greatly cutdown if 
>> the threshold was 2 iso 3.
>>
>> just to make the point, print_r seems to use a threshold of 2 (which 
>> is why I always try print_r before taking my chances with var_dump):
>>
>> <?php
>>
>> class a { public $self; }
>>
>> $A = new a;
>> $A->self = $A;
>> var_dump( $A );
>> print_r( $A );
>>
>> ?>
>>
>>>
>>> HTH,
>>> Andrey
>>>
>>> Francisco M. Marzoa Alonso wrote:
>>>
>>>> BTW., I'm not sure that there's nothing more wrong here. Takin the 
>>>> first part of the code of first example:
>>>>
>>>> <?php
>>>>
>>>> $Arr = array();
>>>> $Arr['self'] = &$Arr;
>>>> var_dump ( $Arr );
>>>>
>>>> ?>
>>>>
>>>> It returns:
>>>>
>>>> array(1) {
>>>> ["self"]=>
>>>> array(1) {
>>>>   ["self"]=>
>>>>   *RECURSION*
>>>> }
>>>> }
>>>>
>>>> Is that as its expected to be? I meant that perhaps it should be:
>>>>
>>>> array(1) {
>>>>   ["self"]=>
>>>>   *RECURSION*
>>>> }
>>>>
>>>> Since the element in $Arr['self'] is yet (or at least should be) a 
>>>> reference to itself...
>>>>
>>>
>>
>