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>

Explanation of the Code

Label and Select Element

<label>: The label is tied to the select box via the for attribute, improving accessibility. It’s crucial for screen readers and a better user experience.

<select>: The multiple attribute allows multiple categories to be selected. The name attribute is set to category_id[] to handle multiple selections properly when the form is submitted.

Rendering the Categories:

@foreach ($categories as $category): This loop iterates over all available categories, generating an <option> element for each.

<option value="{{ $category->id }}">: The value attribute is set to the category’s ID. This is necessary for submitting the selected categories back to the server.

{{ in_array($category->id, $post?->categories->pluck('id')->toArray() ?? []) ? 'selected' : '' }}: This statement checks if the current category ID exists in the list of categories associated with the post.

nullsafe operator (post?): Safely accesses $post->categories even if the $post object is null (e.g., when creating a new post).
pluck('id')->toArray(): Extracts the category IDs associated with the post and converts them into an array.
in_array(): Checks if the current category ID is part of the selected categories. If it is, the selected attribute is added, which pre-selects the category in the dropdown.

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.