Re: Static Class Member References

Richard Quadling wrote: > On 13 July 2010 09:46, Richard Quadling <rquadling@gmail.com> wrote: >> On 12 July 2010 22:54, Daniel Kolbo <kolb0057@umn.edu> wrote: >>> Richard Quadling wrote: >>>> On 11 July 2010 23:19, Daniel Kolbo <kolb0057@umn.edu> wrote: >>>>> Hello PHPers, >>>>> >>>>> I'm having some trouble understanding some PHP behaviour. The following >>>>> example script exhibits the behaviour which I cannot understand. >>>>> [code] >>>>> <?php >>>>> >>>>> class A >>>>> { >>>>> public static $a = 3; >>>>> >>>>> function __construct() >>>>> { >>>>> //self::$a = $this; //[i] >>>>> self::$a =& $this; //[ii] >>>>> } >>>>> } >>>>> >>>>> class B extends A >>>>> { >>>>> function __construct() >>>>> { >>>>> parent::__construct(); >>>>> } >>>>> } >>>>> >>>>> class C { >>>>> var $c; >>>>> >>>>> function __construct() >>>>> { >>>>> $this->c =& A::$a; >>>>> } >>>>> >>>>> } >>>>> >>>>> >>>>> $c = new C; >>>>> $b = new B; >>>>> $cee = new C; >>>>> >>>>> var_dump($c->c); // [i] prints object(B), but [ii] prints int 3 >>>>> var_dump($cee->c); // [i] prints object(B), and [ii] prints object(B) >>>>> >>>>> ?> >>>>> [/code] >>>>> >>>>> Why does $c->c print 'int 3' ? >>>>> >>>>> I'm nervous to use "self::$a = $this;" because I don't want >>>>> to be >>>>> copying the whole object. However, isn't $this just a reference to the >>>>> object, so "self::$a = $this;" is just copying the reference and not >>>>> the >>>>> actual object, right? >>>>> >>>>> Thanks in advance >>>> >>>> What do you think the value should be? >>>> >>>> A static property is bound to the class and not to an instance of the class. >>>> >>>> So, &A::$a is a reference to the static value. If you alter the value, >>>> it will be altered for a subclasses of A and for any other reference >>>> to it. >>>> >>> I think >>> var_dump($c->c); would print object(B), but it's printing int 3. >>> >>> The reference is *not* being updated. I think this is a bug. What do >>> you think? >>> >>> Thanks > > Aha! > > $c = new C; > > At this stage $c->c will be a reference to the static A::$a = 3. > > $b = new B; > > Now, as B's constructor calls A's constructor which replaces the > static A::$a with a reference to the instance $b, the static A::$a > should now be $b > > $cee = new C; > > At this stage $cee->c will be a reference to the static A::$a = $b. > > But, when var_dump()'d, $c->c !== $cee->c, and I think they should as > both have been assigned to a reference of a static. > > It would seem to be a bug. > > I get the same output for V5.0.0 to V5.3.3RC2 > Thanks for confirming. I reported the bug. I shortened up the test script quite a bit. Please see: Bug #52332 http://bugs.php.net/bug.php?id=52332 `