PHP - How To Delete An Object?

I thought I was deleting (unset) an object, but when adding a destructor, found it was never being fired.  I then used debug_zval_dump() and found that my refcount is 7, and it is my understanding that it must be 3 (more on why I think this later).

I searched where I might have left a copy, but couldn't find it.  Any recommendations how to do so?  I looked for ways to find all references to an object

After manually searching and not finding exactly what I was looking for, I came across this script.

    public function addGatewayClient(GatewayClient $client):TimerInterface
    {
        return $this->loop->addPeriodicTimer($this->period, function() use($client) {
            // bla bla bla
        });
    }

To verify whether a reference was being created, I wrote the below script.

<?php
ini_set('display_errors', 1);

class MyClass
{
    public function __destruct()
    {
        echo('__destruct'.PHP_EOL);
    }    
}

function getZval($v):string {
        ob_start();
        debug_zval_dump($v);
        $rs = ob_get_clean();
        return str_replace(PHP_EOL, '', $rs);
}

$obj = new MyClass;
echo('create object: '.getZval($obj).PHP_EOL);
$objC1 = $obj;
echo('save first reference: '.getZval($obj).PHP_EOL);
$objC2 = $obj;
echo('save second reference: '.getZval($obj).PHP_EOL);

// This is the line to comment out
$func = function() use($obj) {};

echo('set function: '.getZval($obj).PHP_EOL);

unset($objC1);
echo('delete first reference: '.getZval($obj).PHP_EOL);

unset($objC2);
echo('delete second reference: '.getZval($obj).PHP_EOL);

unset($obj);

echo('Done'.PHP_EOL);

If I comment out \\$func = function() use($obj) {};, I see the refcount start at 3, go up to 5 and then back down to 3, then __destruct() being called, and then the script completion "Done".  But then when I don't comment the closure function, I see it go up to 6, go down to 4, the script completion "Done", and then __destruct() being called.

Guess I can just set the object to be deleted to NULL, but I feel there should be a better way.  Any recommendations?

On a side note, debug_zval_dump() is more difficult in the real world if there is recursion, and my getZval() function results in a fatal error by exhausting too much memory.  I also tried just calling debug_zval_dump(), but it definitely wasn't a good call.