多个选择字段 - 选择字段必须是一个数组，$ request输出中只显示一个<option>

Question

I have the code below that is a resume of the process to create a new conference. To create a new conference is ncessary that the user introduce some info like the conference name, etc. The user also needs to introduce between 1 and 3 categories for the conference.

So there is a select element using select2 plugin so the user can select the categories:

<div class="form-row">
    <div class="form-group col-lg-6">
        <label for="categories">Category</label>
        <select id="tag_list" required  multiple class="form-control" value="{{ old('categories') }}" name="categories" id="categories">
            @foreach($categories as $category)
                <option value="{{$category->id}}">{{$category->name}}</option>
            @endforeach
        </select>
    </div>
</div>

Then the laravel code to store the conference info and also the categories of the conference in the conference_category table since there is a many to many relationship between confernece and category:

public function store(Request $request)
    {
        $this->validate($request, [
            'conference_name' => 'required|max:255|string',
            'conference_categories' => 'required|array|between:1,3|integer',
        ]);

        $conference = Conference::create([
            'name' => $request->conference_name,
        ]);

        $conference->categories()->attach($request->conference_categories);
    }

The select2 JS:

$(function() {
    $('#tag_list').select2({
        placeholder: '',
        dropdownAutoWidth: 'true',
        width: '100%'
    });
});

Errors

• If the user selects more than one category in the $request output just appears the id of one category
• And it appears a laravel validation error after submit the form "The conference categories must be an array. "

Do you know where can be the issue?

Answer 1

You gotta change the name attribute of your select to an array, like this and also remove one id attribute from it, it can't have 2

<select required  multiple class="form-control" value="{{ old('categories') }}" name="categories[]" id="categories">