[PHP] Passing Multilayered Objects, by Reference, to Independent Sub-Objects

[Andrew Immerman]

Hello,

The example that follows this little description should, as far as my
understanding of PHP goes, demonstrate proper passing of multilayered
objects, by reference, to independent sub-objects.  The more understandable
description, there exists a super-class that has two sub-classes.  The first
sub-class, upon construction, is linked to the second sub-class (via a
parameter passed to the first class' constructor).  The first sub-class'
constructor sets a variable, local to that first sub-class, to be a
reference to the second sub-class.  The second sub-class is comprised only
of a variable that will be changed by functionality defined in the first
sub-class.

The first code snippet does not function properly.  It seems that the first
sub-class does not truly create a reference, but creates a copy of the
second sub-class (as it exists upon construction of the first sub-class).
Therefore, it can not be changed, only read.

The second code snippet functions properly and implements what I label a
hack around.  This code snippet accesses the second sub-class within the
constructor of the first sub-class.  In other words, it seems that PHP does
not create a reference, unless something within that reference is accessed
within the function defining the reference.  <<Confusing, ain't it.>>

Please tell me if there is a more "correct" solution, or if I'm simply
confused to oblivion. =)

--- [FIRST CODE SNIPPET] ---

<?
        class Test0_t
        {
                var $oTest1;
                var $oTest2;

                function Test0_t ()
                {
                        $this->oTest1 = new Test1_t($this);
                        $this->oTest2 = new Test2_t();
                }
        }

        class Test1_t
        {
                var $oLnk;

                function Test1_t ( &$_oLnk )
                {
                        $this->oLnk = &$_oLnk;
                }

                function Test ()
                {
                        echo("0:[".$this->oLnk->oTest2->nVal."]<BR>");
                        $this->oLnk->oTest2->nVal++;
                        echo("1:[".$this->oLnk->oTest2->nVal."]<BR>");
                }
        }

        class Test2_t {
                var $nVal;

                function Test2_t ()
                {
                        $this->nVal = 0;
                }
        }

        $oTest0 = new Test0_t();

        $oTest0->oTest1->Test();

        echo("2:[".$oTest0->oTest2->nVal."]<BR>");
?>

--- [SECOND CODE SNIPPET] ---

<?
        class Test0_t
        {
                var $oTest1;
                var $oTest2;

                function Test0_t ()
                {
                        $this->oTest2 = new Test2_t();
                        $this->oTest1 = new Test1_t($this);
                }
        }

        class Test1_t
        {
                var $oLnk;

                function Test1_t ( &$_oLnk )
                {
                        $this->oLnk = &$_oLnk;
                        $this->oLnk->oTest2->Test();
                }

                function Test ()
                {
                        echo("0:[".$this->oLnk->oTest2->nVal."]<BR>");
                        $this->oLnk->oTest2->nVal++;
                        echo("1:[".$this->oLnk->oTest2->nVal."]<BR>");
                }
        }

        class Test2_t {
                var $nVal;

                function Test2_t ()
                {
                        $this->nVal = 0;
                }

                function Test ()
                {
                }
        }

        $oTest0 = new Test0_t();

        $oTest0->oTest1->Test();

        echo("2:[".$oTest0->oTest2->nVal."]<BR>");
?>

Thank you,
-Andrew Immerman


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