[PHP-DOC] #20760 [Com]: strange behaviour regarding $this From: wb <email protected>
Date: 12/03/02

 ID: 20760
 Comment by: wb <email protected>
 Reported By: krennmair <email protected>
 Status: Open
 Bug Type: Documentation problem
 Operating System: RedHat 8.0
 PHP Version: 4.2.2
 New Comment:

i once had made the same 'mistake': i had split up a inheritance chain
at some place but then i needed a function of the other inheritance
trtee after the split. in fact, it worked out fine - so fine that i
even didnīt notice that the superclass call was outside the inheritance
chain. when i later noticed it i removed it because i got worried if it
was desired behaviour or if it could disappear in some later version of
php. but if you tell me that i can rely on it i will use it.

Previous Comments:
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[2002-12-02 05:17:04] krennmair <email protected>

OK, but mark it in the documentation with a big red callsign. ;-)

But what I'm still interested in, is _why_ this is intended. The only
reason I can think of is to confuse other programmers, but that would
be absurd.

------------------------------------------------------------------------

[2002-12-02 04:29:18] derick <email protected>

This is indeed intended behavior, but it should be documented. I have
some logs about this, but can not find them now.

Derick

------------------------------------------------------------------------

[2002-12-02 04:24:24] krennmair <email protected>

We have found a strange behaviour regarding $this. One of our
programmers made a mistake during programming, which led to
"Heisenbugs", which were not quite easy to find and fix. We could
reduce the problem to a simple program to present it:

<?

class Foo {

  var $bla;

  function quux() {
    $this->bla = 5;
  }

}

class Bar {

  var $bla;

  function do_stuff() {
    $this->bla = 10;
    Foo::quux();
    echo $this->bla;
  }
}

$blabla = new Bar;

$blabla->do_stuff();

?>

The output is: "5"

Obviously, Bar::do_stuff() is not allowed to call Foo::quux() since
Foo::quux() is using $this. Now the strange thing comes: instead of
casting an error, PHP happily accepts the code. But the $this in
Foo::quux is the same $this as in Bar::do_stuff(), i.e. $blabla, and
that's why the output is 5. Is this behaviour intended? At least I
couldn't find it documented anywhere. IMO the user should be warned
when $this is used in a static function.

------------------------------------------------------------------------ 

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