When does the class object of PHP be destroyed? How to fix it

When does the class object of PHP be destroyed?
There is a problem, when the object is automatically destroyed, the execution of the script is automatically destroyed, but if I create an object in a function of a, then when the function is finished, object A will automatically destroy it?

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Reference:
Http://school.itzcn.com/special-spid-30.html
The above explanation is more detailed,
Hope that the landlord has helped.
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To be exact, it is recycled after the garbage collector is running .....

Generally no problem, the function will be recycled after the end of ...


But interested can run this program: (


Class A {
function __construct () {
$this->b = new B ($this);
}
function __destruct () {
$this->b->__destruct ();
}
}

Class B {
function __construct ($parent = NULL) {
$this->parent = $parent;
}
function __destruct () {
unset ($this->parent);
}
}

function Test () {
for ($i = 0; $i < 10000; $i + +) {
$a = new A ();
$a->__destruct (); See how this line of comments differs from not commenting
}
}

Test ();
Echo Number_format (Memory_get_usage ());


Comments and not commenting the result of the above line is completely different.

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