Codeigniter 转换从数据库返回的多维数组数据

我在处理多维数组数据时遇到问题。 我加入了两个表（maincategories和categories）

表2主要类别： id，主类别

    $this->db->select('m.id, m.name_en AS maincategory')
            ->select('c.name_en AS category')
            ->from('categories AS c')
            ->join('maincategories AS m', 'c.maincategory_id=m.id', 'left');
    $query = $this->db->get();

表格类别： id，主类别\u id，类别

    $this->db->select('m.id, m.name_en AS maincategory')
            ->select('c.name_en AS category')
            ->from('categories AS c')
            ->join('maincategories AS m', 'c.maincategory_id=m.id', 'left');
    $query = $this->db->get();

这导致下面列出了所有4个类别

[3] => stdClass Object
    (
        [id] => 7
        [maincategory] => Career
        [category] => Business Sales
    )

[4] => stdClass Object
    (
        [id] => 1
        [maincategory] => Accommodation
        [category] => Camping
    )

[5] => stdClass Object
    (
        [id] => 6
        [maincategory] => Accommodation
        [category] => Hostels
    )

[6] => stdClass Object
    (
        [id] => 7
        [maincategory] => Career
        [category] => Career Events
    )

列表中有4个独特的类别，2个属于main类别：住宿，其他2个类别属于main类别：职业。我想实现的是每个主要类别只列出一次，并且这些类别应属于该主要类别。大概是这样的：

[6] => stdClass Object
    (
        [id] => 7
        [maincategory] => Career
        [category] => array(Career Events, Business Sales, .....)
    )
[7] => stdClass Object
    (
        [id] => 7
        [maincategory] => Accommodation
        [category] => array(Hostels, Camping, .....)
    )

function fetch_all(){
    $data  = array();
    $first = $this->db->select('id, maincategory')->get('maincategory')->result_array();
    if( is_array( $first ) && count( $first ) > 0 ){
        foreach( $first as $key => $each ){
           $data[$key]['category_id']   = $each['id']; #main category id
           $data[$key]['maincategory']  = $each['id']; #main category name
           $second  = $this->db->select('category')->where_in('maincategory_id', $each['id'])->get('categories')->result_array();
           $data[$key]['category']      = $second;     #all sub-category(s) array
        }
    } 
}

阵列转储的最终结果可能会有所不同，但我希望您理解我试图实现的目标。我读了很多关于转换多维数组的书。我只是还没想好。非常感谢您的指导

试着这样做：

[6] => stdClass Object
    (
        [id] => 7
        [maincategory] => Career
        [category] => array(Career Events, Business Sales, .....)
    )
[7] => stdClass Object
    (
        [id] => 7
        [maincategory] => Accommodation
        [category] => array(Hostels, Camping, .....)
    )

function fetch_all(){
    $data  = array();
    $first = $this->db->select('id, maincategory')->get('maincategory')->result_array();
    if( is_array( $first ) && count( $first ) > 0 ){
        foreach( $first as $key => $each ){
           $data[$key]['category_id']   = $each['id']; #main category id
           $data[$key]['maincategory']  = $each['id']; #main category name
           $second  = $this->db->select('category')->where_in('maincategory_id', $each['id'])->get('categories')->result_array();
           $data[$key]['category']      = $second;     #all sub-category(s) array
        }
    } 
}

---

不要使用太多的db调用，请尝试使用下划线.php库

我在这里概述了一些如何在本案例中使用它的示例：

编辑