从模型中检索时，Laravel显示“string（）”

In laravel i do the follwing query:

$courses = Curs::where('gruppe', "=", "fredag-wills")->get();

When i run $courses->gruppe it will return string(12) "fredag-wills" instead for fredag-wills why?

here is the var_dump($courses); result

   object(Illuminate\Database\Eloquent\Collection)#244 (1) {
  ["items":protected]=>
  array(15) {
      ["attributes":protected]=>
      array(12) {
        ["id"]=>
        string(2) "48"
        ["keyid"]=>
        string(33) "wills-fredag-1-souvkimjmvpqdwsckh"
        ["endtime"]=>
        string(8) "12:50:00"
        ["parallel"]=>
        string(1) "0"
        ["gruppe"]=>
        string(12) "fredag-wills"
        ["booked"]=>
        string(1) "0"
      }

Those string are just plotted by var_dump so you can see every variable type, if you don't want to see them while debugging, you can do this:

$courses = Curs::where('gruppe', "=", "fredag-wills")->get();

foreach($courses as $course)
{
   echo $course->keyid . '<br>';
}

die;