$this->_product->collCount()

$filter['where'] = ['in', 'category', $category_id];

这个代码是你自己写的，还是fecshop源码这样写的？

$category_id必须是数组才行，Yii2没有用过？基本语法！

如果直接查询单个分类：

$filter['where'] = ['category' => $category_id]; 

@Terry #1楼 $category_id就是数组

函数有注释仔细看

/*
     * @property $filter | Array ， example filter:
     * [
     * 		'numPerPage' 	=> 20,
     * 		'pageNum'		=> 1,
     * 		'orderBy'	=> ['_id' => SORT_DESC, 'sku' => SORT_ASC ],
     * 		'where'			=> [
                ['>','price',1],
                ['<=','price',10]
     * 			['sku' => 'uk10001'],
     * 		],
     * 	'asArray' => true,
     * ]
     * 得到总数。
     */
    public function collCount($filter = '')
    {
        $query = $this->_productModel->find();
        $query = Yii::$service->helper->ar->getCollByFilter($query, $filter);
        return $query->count();
    }

直接告诉你把

$filter['where'][] = ['in', 'category', $category_id];

@Terry #4楼 哦哦

@Terry #4楼 laravel用多了

@fecshoper [#6楼](#comment6) yii2也是这样的，是没有问题的，是Fecshop进行封装了