Create Excel matrix with PHPExcel (maatwebsite/excel) and Laravel 9 from Mysql data

I am trying to create an Excel file from my Database that looks like this :

I have 3 tables : a User table, a Group Table, and a Group Matching table that is martching user_id and group_id as a user can have many groups.

I successfully constructed the header dynamically by querying the group list and appening "User Name" and "User Lastname" to the header array

public function headings(): array
    {
        $header = array();
        $search ="Group";
        $groupList = new \App\Models\Group;
        $groupList = $groupList::where('name','LIKE',"%{$search}%")->get();;
        foreach($groupList as $key=>$value)  {
            $header[]=$value["name"];    
        }
        array_unshift($header,"User Name", "User Lastname");

        return $header;
    }

note that I cannot control the number of group that will be output.

Next, I have my collection of records that are returning an array that contains user names, lastnames, and group membership.

    public function array(): array
    {
        $datas = array();
        $MyUsers = MyUser::with(['groupMatching'])->get();
        foreach($MyUsers as $MyUser) {
           
            $datas[$MyUser->id]["name"] = $MyUser->lastname;
            $datas[$MyUser->id]["firstname"] = $MyUser->firstname;
            foreach($MyUser->groupMatching as $MyMember) {
                $datas[$MyUser->id]["groups"][]  = $MyMember->Group_name;

            }

            
        }
        return $datas;
    }

so $datas looks like this :

array:23 [▼ // app/Exports/MyUsersExport.php:31
  4 => array:3 [▼
    "name" => "Doe"
    "firstname" => "John"
    "groups" => array:3 [▼
      0 => "Group A"
      1 => "Group X"
    ]
  5 => array:3 [▼
    "name" => "Jane"
    "firstname" => "Doe"
    "groups" => array:2 [▼
      0 => "Group X"
    ]
  ]
  ]

What's the next step to achieve the illustrated output? How can I get an X on matching column name / datas ?

I tried to look around for map functions and some examples but could not find the way to go. I am using laravel 9 and maatwebsite/excel 3.1

Thank you for your help :)

Since you don't have the ability to set a row value for a specific column, I would suggest declaring the $groupList variable in the class, then filling it in the headings method. Then in the array method you cycles all the groups and do a search if the user belongs to that group.

public function array(): array
{
    $datas = array();
    $MyUsers = MyUser::with(['groupMatching'])->get();

    foreach($MyUsers as $MyUser) {
        $datas[$MyUser->id][] = $MyUser->lastname;
        $datas[$MyUser->id][] = $MyUser->firstname;

        foreach ($this->groupList as $groupItem) {
            $exists = (bool) $MyUser->groupMatching->firstWhere('Group_name', $groupItem['name']);

            $datas[$MyUser->id][] = $exists ? 'X' : '';
        }
    }

    return $datas;
}