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...
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