Description:
------------
When overwriting an old signal handler (that references "$this" for example) with SIG_DFL, the reference counter on $this is not decreased, so when unsetting the object, it cannot be freed.

My current workaround: When overwriting the signal handler with an empty function before ("function() {}"), the ref-count is correctly decreased (WTF?!), and the instance is immediately freed, when unsetting the object.

Test script:
---------------
class Test {
    public function __construct() {
        pcntl_signal(SIGUSR1, array($this, 'signalHandler'), false);
        //pcntl_signal(SIGUSR1, function() {}); // destruct works correctly when commenting in
        pcntl_signal(SIGUSR1, SIG_DFL);
    }

    public function signalHandler() {
    }

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

$test = new Test();

echo 'unsetting' . PHP_EOL;
unset($test);
echo 'end' . PHP_EOL;


Expected result:
----------------
unsetting
__destruct
end

Actual result:
--------------
unsetting
end
__destruct