library/Rediska/Zend/Session/SaveHandler/Redis.php
public function destroy($id)
    {
        try {
            $this->_set->remove($id);
        } catch(Rediska_Connection_Exec_Exception $e) {
            $this->_deleteSetOrThrowException($e);
        }

        return $this->getRediska()->delete($this->_getKeyName($id));
    }
public function destroy($id)
    {
        try {
            $this->_set->remove($id);
        } catch(Rediska_Connection_Exec_Exception $e) {
            $this->_deleteSetOrThrowException($e);
        }

        return $this->getRediska()->delete($this->_getKeyName($id));
    }
Destroy session

@param string $id
@return boolean