php destructor behaviour

Question

im trying to understand php constructor and destructor behaviour. Everything goes as expected with the constructor but i am having trouble getting the destructor to fire imp

Answer 1

The __destruct method of a class is called once all references to the object are unset.

For example

$dummy = (object) new Class();

The destructor is automatically called if the dummy object is set to null or the script is exited.

unset($dummy); // or $dummy = null;
//exit(); //also possible

However, there are three crucial memory notes to calling the destructor method:

Firstly, the desctructor method should be a public method, not protected or private.

Secondly, refrain from using internal and circular references. For example:

class NewDemo
{
     function __construct()
     {
          $this->foo = $this;
     } 
     function __destruct()
     {
          // this method will never be called 
          // and cause memory leaks
          // unset will not clear the internal reference
     }
}

The following will not work either:

$a = new Class();
$b = new Class();
$a->pointer = $b;
$b->pointer = $a;

unset($a); // will not call destructor
unset($b); // will not call destructor

Thirdly, deciding whether destructors are called after output is sent. Using

gc_collect_cycles() 

one can determine whether all destructors are called before sending data to user.

See http://php.net/manual/en/language.oop5.decon.php for the sources and elaborate explanations of magic destruct methods with examples.