[BUG]: Incorrect return type hint of Phalcon\Mvc\Model\Criteria::getColumns()

[sergeyklay]

Current return type hint of the Phalcon\Mvc\Model\Criteria::getColumns implies that method must return a string or just null:

cphalcon/phalcon/Mvc/Model/Criteria.zep

Lines 334 to 343 in 5c34a6c

	public function getColumns() -> string | null
	{
	var columns;
	if !fetch columns, this->params["columns"] {
	return null;
	}
	return columns;
	}

But it MAY return an array:

$criteria = new Criteria();
$criteria->columns(['id' => 'inv_id', 'total'  => 'inv_total']);

// ['id' => 'inv_id', 'total'  => 'inv_total']
$criteria->getColumns();

This leads to a fatal error:

PHP Fatal error:
Return value of Phalcon\Mvc\Model\Criteria::getColumns()
must be of the type string or null, array returned in Unknown on line 0

[sergeyklay]

Fixed in 4.0.x branch