undefined variable when trying to fetch data from database laravel

I can tell you're learning Laravel. There are several issues with the code posted in your question. Let's walk through each of these to see if we can improve your understanding.

First, let's take a look at the controller method signature:

public function getData($id) 

This method expects an $id parameter defined in the corresponding route. However, if we take a look at the route:

Route::get('/home/(:any)', 'HomeController@getData')->name('home'); 

...it doesn't properly declare that the URL contains a parameter (the video you're watching is about a very old version of Laravel). As described in the docs, we'll need to change the route signature to include a parameter for $id:

Route::get('/home/{id}', 'HomeController@getData')->name('home');

Next, let's see how the controller method fetches its data:

$data['data'] = DB::table('personal_infos')->get()->sortByDesc('upload_time');

This query fetches all records from personal_infos into a Collection, and then sorts them by upload_time. This is fine, but database engines can usually sort data faster than our PHP application, so we can instruct the DB to sort our data for us:

$data['data'] = DB::table('personal_infos')->orderBy('upload_time', 'desc')->get();

Notice how we changed the call to sortByDesc() on the collection to orderBy() for the database query. Now, the database sorts the results for us, so the collection doesn't need to.

Finally, let's try to fix the error you experience when passing the data to the view. Here's how your controller method currently does it:

if (count($data) > 0) {
    return view('home', $data)
        ->with('test', personal_info::find($id)); // --> after adding this got error
} else {
    return view('home');
}

There are a couple problems with the code above:

1. count($data) will always be greater than zero, because we're setting $data['data'] every time we call the method, so the else block will never execute. This is probably fine because...
2. ...when count($data) equals zero, the controller doesn't pass the view any data, so $data in the view will be undefined.

The view in question uses @foreach to loop through each of the results, so we can simplify the code in the controller method because foreach won't iterate over an empty collection:

$personalInfos = DB::table('personal_infos')->orderBy('upload_time', 'desc')->get();

return view('home') 
    ->with('personalInfos', $personalInfos) 
    ->with('test', personal_info::find($id));

The view will receive two variables from the method above: $personalInfos and $test. I took the liberty of renaming $data['data'] into a more meaningful variable. This becomes very important as the project grows. Here's how we can use the data in the view:

<ul>
    @foreach ($personalInfos as $info) 
        <li>{{ HTML::link_to_route('home', $info->Name, [ $info->id ]) }}</li>
    @endforeach 
</ul>

The template above outputs an unordered list as shown in the image in the question. The original table contains several row/column nesting errors and will not display the information like the question describes. As we can see, this template loops through each result in $personalInfos. If $personalInfos is empty, the list will not display any items.

If we want our controller method to handle the route with or without an ID, we'll need to tell Laravel that the ID is optional. For the route, a question mark (?) after the parameter makes it optional:

Route::get('/home/{id?}', 'HomeController@getData')->name('home');

Then, we can set a default value for the controller method that handles the route. In this case, we'll use null:

public function getData($id = null) 

Of course, after we update this, we'll need to change the method to handle a null $id argument, which we use to fetch a personal_info for the view's $test variable. The question doesn't explain how the view uses $test, so I'll leave this as an exercise to the reader :)