How to show old selected values in multiple select options in Laravel

When creating a form to manage posts and their associated categories, especially with a many-to-many relationship, it's important to show previously selected categories. This ensures users can see and manage their current selections when updating a post.

Below is a refined approach to achieve this in a Laravel Blade template.

<div class="mb-3">
    <label class="form-label" for="category">Category</label>
    <select class="form-control" id="category" name="category_id[]" multiple>
        @foreach ($categories as $category)
            <option value="{{ $category->id }}"
                {{ in_array($category->id, $post?->categories->pluck('id')->toArray() ?? []) ? 'selected' : '' }}>
                {{ $category->name }}
            </option>
        @endforeach
    </select>
    @error('category_id')
        <span class="pt-3 text-danger">{{ $message }}</span>
    @enderror
</div>

Benefits of This Approach

Clarity: Clearly shows which categories are selected based on the post object.

Flexibility: Handles both creating and updating posts with selected categories.

Error Display: Properly shows validation errors related to category selection.