Question

I have spot the following pattern in code I’m working with: in some classes in destructor I have found private variable being nulled, in example:

public function __destruct()
{
    foreach($this->observers as $observer)
    {
        $observer = null;
    }
    $this->db_build = null;
}

Is there any point in doing this when PHP has GC? Does it somehow improve performance of script?

Answer 1

It could be because PHP’s garbage collection is based on reference countring, and older versions could not handle cyclical dependencies. Then, in some cases it would have been necessary to manually set references to null to enable the GC to do its work, and there may still be some special cases that the cycle detection algorithm does not catch.

More likely though, it’s just an example of cargo cult programming (the Wikipedia entry even explicitly lists this as an example).