Laravel存储数据自动增量

Question

class PostController extends Controller{
   public $grupID = 1;
   public function store(Request $request)
   {
      $post = new Post();
      $post->GroupID = 'POST-' . $this->grupID;
      $post->save();
      return response()->json($post);
      $this->grupID++;
   }
}

Database Structur

public function up()
{
    Schema::create('posts', function (Blueprint $table) {
        $table->increments('id');
        $table->integer('PostTypeID');
        $table->string('GroupID', 100)->nullable();
        $table->timestamps();
    });
}

I want to make the groupID auto increment, but it always return 'POST-1'.

Answer 1

class PostController extends Controller{
   public function store(Request $request)
   {
      $last = DB::table('posts')->last();
      $post = new Post();
      if ($last) {
         $part = explode('-', $last->GroupID);
         $post->GroupID = $part[0] . '-' . ($part[1] + 1);
      } else {
         $post->GroupID = 'POST-1';
      }
      $post->save();
      return response()->json($post);
   }
}