Convert filters of Collection to array

[baijunyao]

The default value of filters is null when used as a parameter, An error is thrown when executing the array_merge function.

stripe-php/lib/Collection.php

Lines 180 to 184 in e4da443

	$params = array_merge(
	$this->filters,
	['starting_after' => $lastId],
	$params ?: []
	);

[ob-stripe]

Hi @baijunyao, thanks for the contribution.

filters should never be null -- it's initialized with an empty array, not null:

stripe-php/lib/Collection.php

Line 22 in 4b245d2

protected $filters = [];

That said, I just modified this class' code (for unrelated reasons) in #797 and I added a safeguard so that the array_merge calls will succeed even if filters is null for some reason:

stripe-php/lib/Collection.php

Lines 195 to 196 in 4b245d2

	$params = array_merge(
	$this->filters ?: [],

.

Closing this, but feel free to reply if you believe there's still a bug in stripe-php!

[baijunyao]

Sorry, I didn't say it clearly. I mean that filters in the parameter is null by default.

stripe-php/lib/Collection.php

Lines 66 to 80 in e4da443

	public function all($params = null, $opts = null)
	{
	self::_validateParams($params);
	list($url, $params) = $this->extractPathAndUpdateParams($params);
	list($response, $opts) = $this->_request('get', $url, $params, $opts);
	$obj = Util\Util::convertToStripeObject($response, $opts);
	if (!($obj instanceof \Stripe\Collection)) {
	throw new \Stripe\Exception\UnexpectedValueException(
	'Expected type ' . \Stripe\Collection::class . ', got "' . get_class($obj) . '" instead.'
	);
	}
	$obj->setFilters($params);
	return $obj;
	}

The following line of code will set $this->filters to null.

$obj->setFilters($params);

stripe-php/lib/Collection.php

Lines 46 to 51 in e4da443

	public function setFilters($filters)
	{
	$this->filters = $filters;
	unset($this->filters['starting_after']);
	unset($this->filters['ending_before']);
	}

The following code will report an error array_merge() expects parameter 1 to be array, null given.

    foreach (\Stripe\Account::all()->autoPagingIterator() as $payout) {
        var_dump($payout);
    }

The $this->filters ?: [] you added two hours ago solved this issue.
But array_key_exists can't accept null values either.
So I opened a new PR #798 to fix the issue.