Weak references provide a non-intrusive gateway to ephemeral objects. Unlike normal (strong) references, weak references do not prevent the garbage collector from freeing that object. For this reason, an object may be destroyed even though a weak reference to that object still exists. In such conditions, the weak reference seamlessly becomes invalid.
Пример #1 Weakref usage example
<?php
class MyClass {
public function __destruct() {
echo "Destroying object!\n";
}
}
$o1 = new MyClass;
$r1 = new Weakref($o1);
if ($r1->valid()) {
echo "Object still exists!\n";
var_dump($r1->get());
} else {
echo "Object is dead!\n";
}
unset($o1);
if ($r1->valid()) {
echo "Object still exists!\n";
var_dump($r1->get());
} else {
echo "Object is dead!\n";
}
?>
Результат выполнения данного примера:
Object still exists!
object(MyClass)#1 (0) {
}
Destroying object!
Object is dead!