Get a array of values form a PLSQL Function

I coded a function to select some flux in a queue and lock them with an updated flag. I made it with a cursor and it worked great. But i need to get the ID of the flux i locked to process them in my application.

So i start to code a function:

CREATE OR REPLACE Function getIDArray
  RETURN VARCHAR2 is
  arr varchar2(1000);

          CURSOR flux_to_process                                                          
          IS                                                                              
           SELECT  FLUX_ID, LOCKED_FLAG
           FROM (
               SELECT FLUX_ID, FLUX, GROUP_STORE_ID, STORE_ID, REFID, FLUX_TYPE, LOCKED_FLAG
                 FROM DEV_ISB_TRANSACTIONS.BUFFER_FLUX                                      
                 WHERE status = 0                                                           
                 AND LOCKED_FLAG = 0                                                                                                             
                 ORDER BY DATE_CREATION ASC)
            WHERE ROWNUM <= 8;

          BEGIN                                                                           

          FOR flux_rec IN flux_to_process                                                 
              LOOP                                                                        
              IF flux_rec.LOCKED_FLAG = 0
                THEN      

                UPDATE DEV_ISB_TRANSACTIONS.BUFFER_FLUX                                    
                SET LOCKED_FLAG = 1                                                         
                WHERE FLUX_ID = flux_rec.FLUX_ID; 
                arr := flux_rec.FLUX_ID;

              else exit;
          COMMIT;                                                                         
          END IF;
          END LOOP; 
          RETURN arr;
         END;

The function compilation return an OK but i got no return of my values.

Do you guys have any clue to how to do this ?