What you mean under "forever in memory"?

[Shkarbatov]

Hi, trying to understand this slide: https://speakerd.s3.amazonaws.com/presentations/8f6d8303502241cab85a320a2bb1db2d/slide_27.jpg

What you mean under "forever in memory"?

If I try next:

class MyClass{}

function buildObjects() {
    $objectA = new MyClass();
    $objectB = new MyClass();

    $objectA->b = $objectB;
    $objectB->a = $objectA;

    return $objectA;
}

$leakHolder = [];
for ($i = 0; $i < 200; $i++) {

    $object = buildObjects();
    $leakHolder[] = $object;
}

unset($leakHolder);
unset($object);
meminfo_dump(fopen('/tmp/php_mem_dump'.$i.'.json','w'));

With iterations: 200, 2 000, 20 000, 200 000

---

Result always the same:

| Type    | Instances Count | Cumulated Self Size (bytes) |
+---------+-----------------+-----------------------------+
| string  | 82              | 4643                        |
| array   | 9               | 648                         |
| integer | 4               | 64                          |
| unknown | 2               | 32                          |
| float   | 1               | 16                          |
+---------+-----------------+-----------------------------+

What you mean under "always stay in memory"?

As I understand memory will leak until not start cycle GC or until I not run gc_collect_cycles(). We can find only what developer forget to unset.

[BitOne]

This slide explains that without a garbage collector for cycling reference, the objects would stay forever in memory. That was the behavior of pre PHP 5.3, when only the reference counter was managing the memory.

Now we have the GC, this will not happen unless you have a real memory leak.