include('../API.php');

$response = $api->get('/levels');
$response = unserialize($response);


$response=$response['levels']['level'];


$json_membership = [];

for($i=0; $i<sizeof($response); $i++){


$json_membership[] = ['id'=>$response[$i]['id'], 'text'=>$response[$i]['name']];

   }

    echo json_encode($json_membership);

$('.memberships').select2({

placeholder: "",
allowClear: true,
width: 'resolve',
language: "es",
    ajax: {
       url: "cursos/ajax_membership.php",
       type: "post",
       dataType: 'json',
       delay: 250,
      data: function (params) {
return {
  searchTerm: params.term
};
 },
 processResults: function (response) {
   return {
     results: response
    };
   },
      cache: false
     }
    });

<label for="membership">
Asociar Membresía
<select class="memberships form-control" id="membership" style="width:100%" name="membership" required>
</select>
</label>