[PHP-DEV] include_stack, function_stack From: Flavien Lebarbé (flavien <email protected>)
Date: 08/31/00

[Repost. It looks like it didn't make it to the list...]

Hello,

We talked a little bit about a "get_include_history" function
that I suggested a couple of days ago. We decided to postpone
the debate until release of 4.0.2. Now that it's done, let's
open the debate and brainstorm ! :-)

As far as debugging/error reporting goes, there are two things
that I consider important and usefull when tracking a bug in PHP
code (same with others) :
1) include_stack
2) function_call_stack

Let's describe how I see them from a user's point of view:

1) get_include_stack() :
This function returns an array of arrays :

array ( array(1,"test.php"), // primary script that php started with
        array(23,"class1.inc"), // on line 23 of test.php, class1.inc
                                // was included
        array(51,"class2.inc") // on line 51 of class1.inc, class2.inc
                                // was included
        );

Note : The name I gave this at first ("get_include_history")
is not appropriate. It would not be an history, but a stack
of the current situation. Example :
--A.php
<?php
include ('B.php');
include ('C.php');
?> 

--
If an error occurs in C.php, the stack does not say
anything about 'B.php' (should it?)

I've read some objections to this, requesting the existence of 
"hide_include_stack()". I am not 100% against it, but I do not
see when it might be usefull. May be an example of 
attack/behaviour_we_do_not_want would convice me ?

2) function_stack() :

The second one is useful in some situations, look :
--division.inc
<? function division($a,$b) {
	return $a/$b;
   }
?>
---main.php
<? include('division.inc');
echo division(1,5);
echo division(1,"aaa");
echo division(8,0);
?>
---

Then, today, you get "division by zero in file 'division.inc' line 2"
That does not help, because the problem is not in that function (you
could check if $b==0 before doing the divide, but that would not 
solve the real problem here). The real problem is in main.php, and 
given this short example it's obvious, but I'm sure all of you have 
already encountered this kind of situation in a more complex 
application.
If we could get :
	Error devide by zero 
	function stack :
		'division(1,"aaa") on main.php line 3'

_That_ would help !

For this one, I do not know if it's OK to let the programmer
have access to it. I personnaly think it's not a good idea,
so I would rather only add it "inside PHP/Zend", and display it
when an error occurs (ie in php_error)

I have a lot of other ideas for debugging tools, but let's discuss
these ones first. :-)

Flavien.

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