Laravel 5.1 finding project owner email with project_id in other table

I am trying to find a users email when I know the project id.

So in my table projects for example I have a record: id: 1 user_id: 6

I know want to find the email of user 6 in my users table: for example: id: 6 email: hello@gmail.com

so as a result I want to get hello@gmail.com

I've tried something like this, but doesn't seem to be working:

$projectOwnerEmail = DB::table('users')
        ->select('email')
        ->where('id', '=', $input['project_id'])
        ->join('projects', 'users.id', '=', 'projects.user_id')
        ->get();

Many thanks!

via Chebli Mohamed