因为你使用Laravel 8，你不能使用withWhereHas（）。所以你可以在你的类中定义一个函数并重用它：

function filterTasks($query, $request)
{
    if ($request->search_name) {
        $query->where('title', 'like', '%' . $request->search_name . '%');
    }

    if ($request->company_id) {
        $query->where('company_id', $request->company_id);
    }
}

然后：

$categories = Category::whereHas('tasks', function ($query) use ($request) {
    $this->filterTasks($query, $request);
})->with([
    'tasks' =>function ($query) use ($request) {
        $this->filterTasks($query, $request);
    }
])->get();

如果你使用Laravel 9或更高版本，你应该使用withWhereHas（）。该方法应用了即时加载，同时检查了条件。它使你的代码更短，更干净，并且没有重复的代码。

$categories = Category::withWhereHas('tasks', function ($query) use ($request) {
    if ($request->search_name) {
        $query->where('title', 'like', '%' . $request->search_name . '%');
    }

    if ($request->company_id) {
        $query->where('company_id', $request->company_id);
    }
})->get();

您可以尝试从两个值中搜索：

if($request->search_name || $request->company_id){
    $searchName = $request->search_name;
    $companyId = $request->has('company_id') ? $request->company_id : false;

    $categories = Category::with(['tasks'])
                    ->whereHas('tasks', function($query) use ($searchName, $companyId) {
                        $query->where('title', 'like', '%' . $searchName . '%');
                        if($companyId) {
                            $query->orWhere('company_id', $companyId);
                        }
                    })->get();
} else{
    $categories = Category::with('tasks')->get();
}

您可以链接where，以便生成的查询最终将具有LIKEAND an =条件：

if($request->search_name || $request->company_id){
            $categories = Category::with(['tasks' => fn($query) => $query->where('title', 'like', '%' . $request->search_name . '%')])
                        ->whereHas('tasks', fn ($query) => 
                        //search_name might be empty, in which case we do not want to compute a costly wildcard comparison that all records will fulfill as long as they are not null
                        if ($request->search_name) {
                            $query->where('title', 'like', '%' . $request->search_name . '%')
                        }
                        //We check whether we need a criteria for company_id
                        if ($request->company_id) {
                            $query->where('company_id', $companyId);
                        }
                        )->get();
}
else{
    $categories = Category::with('tasks')->get();
}