Object Association doubt.

sohdubom · 07-27-2009, 04:58 PM

Hi. I was wondering which one of the samples below would be right to set as object association.

===snippet 01===

PHP Code:


			
$p1 = new Person(10, 'John Doe', '31/07/1967');

$a1 = new Account;

$a1->accountOwner = $p1;

var_dump($a1);

unset($a1);

echo isset($p1) ? '$p1 isset' : '$p1 is not set'; // Person is still set

=============

===snippet 02===

PHP Code:


			
$a1 = new Account;

$a1->accountOwner = new Person(10, 'John Doe', '31/07/1967');

var_dump($a1);

unset($a1);

// both Account and Person are unset here

=============

In snippet 01 objects Person and Account are created separately and then I reference assign Person to Account, $a1->accountOwner = $p1;

In snippet 02 I reference assign Person to Account, $a1->accountOwner = new Person(10, 'John Doe', '31/07/1967'); so that I don't have $p1 explicitly assigned.

The doubt is: which one is considered to be Association?

Thanx in advance

wGEric · 07-27-2009, 08:13 PM

Neither of those are passing a variable by reference.

In snippet 1, $p1 is being copied into $a1->accountOwner. Both variables have their own location within the memory. Put an & in front of the variable and both variables will be using the same location in memory making $a1->accountOwner and $p1 essentially the same whereas before they were two different objects in memory.

PHP Code:


			
$p1->name = 'John';
$a1->accountOwner = &$p1;

$a1->accountOwner->name = 'Bob';
echo $p1->name; // returns 'Bob'

Salathe · 07-27-2009, 08:17 PM

Eric, for PHP 5 and onwards that's simply not true. Objects are assigned by reference; if you wish to assign a copy then use the clone keyword.

sohdubom · 07-27-2009, 08:41 PM

Yes, we don't need the & in PHP5 ... but actually snippet 01 and 02 are not regular Association, but instead the specialized versions: Agregattion and Composition