How to show Validation error for input array? [duplicate]

You should try this:

$validator = Validator::make($request->all(), [
    "start_time.*"  => "required",
]);

Updated Answer

$validator = $request->validate([
    "start_time"    => "required|array|min:10",
    "start_time.*"  => "required",
]);

Your rule has to be like this:

'start_time.*' => 'required'

I tested your situation with below details and everything worked fine.

view :

<form action="{{ route('test.store') }}" method="post">
    {{ csrf_field() }}

    <input type="text" name="start_time[]" class="form-control start_time" value="" >

    <input type="text" name="start_time[]" class="form-control start_time" value="" >

    <button type="submit" class="btn btn-primary">Submit</button>
</form>

@if ($errors->any())
    <div class="alert alert-danger">
        <ul>
            @foreach ($errors->all() as $error)
                <li>{{ $error }}</li>
            @endforeach
        </ul>
    </div>
@endif

controller :

public function store(Request $request)
{
    $request->validate([
        'start_time.*' => 'required'
    ]);

errors when form is blank :

The start_time.0 field is required.
The start_time.1 field is required.