Add multiple select tagging in Laravel 5.5 with Select2. Can be reused with different models. Also keeps old data selected on reload and on edit.

Laravel 5.5 multiple select tagging system.

// The taggable database table

public function up() {
    Schema::create('stateables', function (Blueprint $table) {    // In this case taggables
        $table->increments('id');
        $table->string('stateables_type');             // In this case taggable_type
        $table->integer('stateables_id')->unsigned();  // In this case taggables_id
        $table->integer('state_id')->unsigned();       // In this case tag_id
        $table->timestamps();
    });
}


// This is the Tag model

class Tag extends Model {

    protected $fillable = ['name'];

    // This is a refrence to a diffrent model that has many tags
    public function lawyers() {
        return $this->morphedByMany(Lawyer::class, 'taggable');
    }
}


// This is an example model where it has many tags. 

class Lawyer extends Model {    
    public function tags() {
        return $this->morphToMany(Tag::class, 'taggables');
    }   
}
    
// Th is used in front end to get old data selected from dropdown and keep old data when on page refresh
function isSelected($id){

    if(!($ids=old('state_tags_id'))){
        $ids = $this->tags->pluck('id');
    }

    return collect($ids)
        ->contains($id) ? 'selected' : '';
}
    
    
// This is the create/edit select dropdown with muitple select

<select name="state_tags_id[]" class="form-control state-tags-multiple" multiple="multiple">
    @foreach(\App\Tag::all() as $$tag)
        <option value="{{ $tag->id }}" {{ $lawyer->isSelected($tag->id) }}>
            {{ $tag->name }}
        </option>
    @endforeach
</select>

<script type="text/javascript">
    $(".state-tags-multiple").select2({
        placeholder: "Select a state",
    });
</script>


// This is to store method to save all the tags in table

public function store(Request $request) {

    $this->validate($request, [
        'name'      => 'required|string|max:255',
    ]);

    $lawyer = Lawyer::create([
        'name'  => request('name')
    ]);

    // Attach all the tags to this lawyer
    $lawyer->tags()->sync($request->state_tags_id);

    $lawyer->save;

    return redirect(route('lawyers.index'));
}


// This the update method to update tags in database table

public function update(Request $request, $id) {

    $this->validate($request, [
        'name'      => 'required|string|max:255'
    ]);

    $lawyer = Lawyer::where('id', $id)->first();

    $lawyer->name = $request->name;

    $lawyer->tags()->sync($request->state_tags_id);

    $lawyer->save;

    return redirect(route('lawyers.index'));
}
    
    
// And this is to deletwe the tags when the model is deleted
    
public function destroy(Lawyer $lawyer) {
    try {
        $lawyer->tags()->sync([]);
        $lawyer->delete();
    } catch (\Exception $e) {
        return back();
    }

    return back();
}