访问相关字段

In FileMaker I have (a.o.) two related tables, where Betreuer_id of table "studentpaper" refers to id of table "Betreuer".

With help of FileMaker's PHP API, I want to access a record in "studentpaper" including the releated fields. Howerver, the later poses a problem. Consider the following PHP code:

 $findCommand =& $fm->newFindAllCommand('studentpaper');
 $result = $findCommand->execute();
 $records = $result->getRecords();
 $record = $records[0];
 echo $record->getField('Titel'); // okay
 echo $record->getField('Betreuer_id'); // okay
 echo $record->getField('Betreuer::Name'); 
 // ERROR: get empty string, even related record has a non-empty field

I have expected for "Betreuer::Name" the correct related result, as usually in FileMaker (and as I get in studentpaper's layout). However, I get only an empty string. What am I doing wrong? Does the relation in FileMaker's PHP-API differs from the "usual" FileMaker approach?

In case anybody is interested, I found the solution on my own.

The problem was that the field wasn't defined (in the layout) as normal text input, but as selection field resticted by a value list.

Thus, one needs to access the value not via the usual getField function but by one of the functions related to value lists. In my case, getValueListTwoFields did the job.