symfony - Is there a better way in reversetransform a non reversable string -

i have class:

class usertofullname implements datatransformerinterface {     public function reversetransform($userfullname)     {         //??     }      public function transform($user)     {        return $user->getfullname();     } } 

$user->getfullname() function formulates full name of user

this hard reverse transform cause full name may result many user (if have identical full name)

is there better way on resolving problem?