php - Method doesn't change object array outside it's scope

Problem is, as far as I can tell, in scoping.

In methoddemo() I'm calling methodremoveElement() which removes an element from the array.

Problem is whenremoveElement() method removes soldier from array it's only removed in that method's scope, when I check that array indemo() method after$this->removeElement(); line, the array remains unchanged.

I've tried to return$elements array inremoveElement() method but that doesn't help either and it that case it returns only array not entire updated object.

I've reduced the problem to this minimum example:

class Foo
{
    private array $elements = [];

    public function __construct(int $howMany)
    {
        for ($i = 0; $i < $howMany; $i++) {
            $this->elements[] = random_int(1, 100);
        }
    }


    public function getElements(): array
    {
        return $this->elements;
    }
}

class Demo
{
    public Foo $foo;

    public function __construct(int $howMany)
    {
        $this->foo = new Foo($howMany);
    }

    public function demo(): void
    {
        echo "\nWe start with ", count($this->foo->getElements()), " soldiers in \$foo->elements\n"; 
        $this->removeElement();

        echo "\nWe have ", count($this->foo->getElements()), " soldiers in \$foo->elements\n"; 
    }

    private function removeElement(): void
    {
        $elements = $this->foo->getElements();
        array_splice($elements, 2, 1);
        echo "\nWe have ", count($elements), " soldiers in local \$elements\n"; 

    }
}

$init = random_int(4,10);
$demo = new Demo($init);
$demo->demo();

$remaining = count($demo->foo->getElements());

if ($init-1 !== $remaining) {
    throw new UnexpectedValueException('Wrong number of elements, application is broken');
}
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Which outputs:

We start with 10 soldiers in $foo->elements

We have 9 soldiers in local $elements

We have 10 soldiers in $foo->elements

Fatal error: Uncaught UnexpectedValueException: Wrong number of elements, application is broken in /in/3cnhl:54
Stack trace:
#0 {main}
  thrown in /in/3cnhl on line 54

Process exited with code 255.
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I would expect$foo->elements to have one element less after going throughDemo::removeElement().

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