Object Hierarchies

qazwsx

Hello!

I dealing with the following problem: I want to access objects in a hierarchy with more than two levels, but I cannot access objects on the third level.

Example:

class A
{
	function A()
	{
		$this->bs = array();
	}

var $name;
var $bs;
}

class B
{
	function B()
	{
		$this->cs = array();
	}

var $name;
var $cs;
}

class C
{
	var $name;
}

$a = new A();
$a->name = "A";

$b = new B();
$b->name = "B";
$a->bs[] = $b;

$c = new C();
$c->name = "C";
$b->cs[] = $c;

echo "<br><br>My A '" . $a->name . "'";

$myB = $a->bs[0];

echo "<br><br>My B '" . $myB->name . "'";

$myC = $myB->cs[0];

echo "<br><br>My C '" . $myC->name . "'";

The script responses with the following output:

My A 'A'

My B 'B'

My C ''

How can I access the C - objects?

I am using PHP 4.

jdorsch

The problem is that PHP 4 is pass by copy by default. If you can upgrade to php 5 do it, it will help a lot with complex objects


$a = new a() ;
$a->name = 'fred' ;

// This puts a copy into your array, so now you have two A objects
// one that is inside b, the other is your original
$b->as[] = $a ;

// This modifies the $a outside $b
$a->name = 'monster' ;

// This makes yet another copy of the object from $b
$acopy = $b->as[0] ;


// echos 'monster'
echo $a->name ; 

// echos 'fred'
echo $acopy->name ;

The solution is to learn how to use the '&' operator which will pass by reference. So you want to do something like


$b->as[0] = & $a ;

Make sure and read up on it on php.net in the object documentation.