note 65193 deleted from language.oop5.basic by bjori

Note Submitter: Andreas Blixt Reason: in docs ---- In response to ksam at mail dot ru (and as further, more technical clarification to the explanation below this note): <?php header("Content-type: text/plain"); class myClass { public $value; function __destruct() { echo chr(10) . "* The garbage collector got me (\$class" . $this->value . ")! *" . chr(10); } } $classA = new myClass(); $classA->value = 1; var_dump($classA); // $classA->value shows as 1. $classB = $classA; // There is still only one instance of myClass after this. $classB->value = 2; var_dump($classA); // $classA->value will now show a value of 2. $classRef = &$classA; $classRef->value = "A"; var_dump($classA); // $classA->value will now show a value of "A". // You might expect the following to destroy the class instance, but it won't. // If $classB hadn't been set to point to the class, it actually WOULD have // been unset, because the garbage collector would destroy it. unset($classA); unset($classRef); echo chr(10) . "classA: "; var_dump($classA); // $classA is now NULL. echo "classB: "; var_dump($classB); // $classB is still showing the same old class instance. $classC = new myClass(); $classC->value = "C"; echo chr(10) . "classC: "; var_dump($classC); // Notice how it shows #2 after (myClass). That's the index // of this new instance of myClass, and that's basically what // $classC now contains, not the actual instance of the class. $classB = NULL; // The destructor for what was originally $classA (and until now, $classB) triggers // immediately after this statement. Not because $classB which held the class address // was nullified, but because there is no longer any variable pointing to the class // instance, which means it's virtually irretrievable from within the script. echo chr(10) . "----> Script ends here. <----" . chr(10); ?>