sizeof vs count

gistfile1.txt

sizeof(array('foo'));

  line  #     opcode                           result  operands
  -----------------------------------------------------------------------------
  2     0     EXT_STMT                                 
        1     EXT_FCALL_BEGIN                          
        2     INIT_ARRAY                       ~0      'foo', 0
        3     SEND_VAL                                 ~0, 1
        4     DO_FCALL                                 'sizeof'
        5     EXT_FCALL_END                            
  3     6     RETURN                                   1


count(array('foo'))

Number of oplines:  7

  line  #     opcode                           result  operands
  -----------------------------------------------------------------------------
  2     0     EXT_STMT                                 
        1     EXT_FCALL_BEGIN                          
        2     INIT_ARRAY                       ~0      'foo', 0
        3     SEND_VAL                                 ~0, 1
        4     DO_FCALL                                 'count'
        5     EXT_FCALL_END                            
  3     6     RETURN