yii\elasticsearch\QueryBuilder::buildAndCondition PHP Method

    private function buildAndCondition($operator, $operands)
    {
        $parts = [];
        foreach ($operands as $operand) {
            if (is_array($operand)) {
                $operand = $this->buildCondition($operand);
            }
            if (!empty($operand)) {
                $parts[] = $operand;
            }
        }
        if (!empty($parts)) {
            return [$operator => $parts];
        } else {
            return [];
        }
    }