Get the name of a class related by foreign key to a specified field key. This is generally used to lookup classes involved in one-to-one relationships with the current object.
void getFKClass (string $k)
Get the name of the class related to the field 'book' on the object 'myChapter':
$chapter = $xpdo->getObject('myChapter',12); echo $chapter->getFKClass('book'); // prints "myBook"