References inside the constructor

<?php
class Foo
{
    function Foo($name)
    {
        // create a reference inside the global array $globalref
        global $globalref;
        $globalref[] = &$this;
        // set name to passed value
        $this->setName($name);
        // and put it out
        $this->echoName();
    }

    function echoName()
    {
        echo "<br>",$this->name;
    }
 
    function setName($name)
    {
        $this->name = $name;
    }
}
?>

<?php
$bar1 = new Foo('set in constructor');
$bar1->echoName();
$globalref[0]->echoName();

/* output:
set in constructor
set in constructor
set in constructor */

$bar2 =& new Foo('set in constructor');
$bar2->echoName();
$globalref[1]->echoName();

/* output:
set in constructor
set in constructor
set in constructor */
?>

<?php
// now we will change the name. what do you expect?
// you could expect that both $bar1 and $globalref[0] change their names...
$bar1->setName('set from outside');

// as mentioned before this is not the case.
$bar1->echoName();
$globalref[0]->echoName();

/* output:
set from outside
set in constructor */

// let us see what is different with $bar2 and $globalref[1]
$bar2->setName('set from outside');

// luckily they are not only equal, they are the same variable
// thus $bar2->name and $globalref[1]->name are the same too
$bar2->echoName();
$globalref[1]->echoName();

/* output:
set from outside
set from outside */
?>

<?php
class A
{
    function A($i)
    {
        $this->value = $i;
        // try to figure out why we do not need a reference here
        $this->b = new B($this);
    }

    function createRef()
    {
        $this->c = new B($this);
    }

    function echoValue()
    {
        echo "<br>","class ",get_class($this),': ',$this->value;
    }
}


class B
{
    function B(&$a)
    {
        $this->a = &$a;
    }

    function echoValue()
    {
        echo "<br>","class ",get_class($this),': ',$this->a->value;
    }
}

// try to understand why using a simple copy here would yield
// in an undesired result in the *-marked line
$a =& new A(10);
$a->createRef();

$a->echoValue();
$a->b->echoValue();
$a->c->echoValue();

$a->value = 11;

$a->echoValue();
$a->b->echoValue(); // *
$a->c->echoValue();

/*
output:
class A: 10
class B: 10
class B: 10
class A: 11
class B: 11
class B: 11
*/
?>