original_string: public function getDriver()
      {
          if (null != $this->driver) {
              return $this->driver;
          }
  
          switch($this->config['driver']) {
              case "file":
                  $this->driver   = $this->createFileDriver();
                  break;
              case "memcached":
                  $this->driver   = $this->createMemcacheDriver();
                  break;
              case "redis":
                  $this->driver   = $this->createRedisDriver();
                  break;
              default:
                  throw new SessionException("Driver [{$this->config['driver']}] not supported.");
          }
  
          return $this->driver;
      }
code: public function getDriver()
      {
          if (null != $this->driver) {
              return $this->driver;
          }
  
          switch($this->config['driver']) {
              case "file":
                  $this->driver   = $this->createFileDriver();
                  break;
              case "memcached":
                  $this->driver   = $this->createMemcacheDriver();
                  break;
              case "redis":
                  $this->driver   = $this->createRedisDriver();
                  break;
              default:
                  throw new SessionException("Driver [{$this->config['driver']}] not supported.");
          }
  
          return $this->driver;
      }
code_tokens: public function getDriver ( ) { if ( null != $ this -> driver ) { return $ this -> driver ; } switch ( $ this -> config [ 'driver' ] ) { case "file" : $ this -> driver = $ this -> createFileDriver ( ) ; break ; case "memcached" : $ this -> driver = $ this -> createMemcacheDriver ( ) ; break ; case "redis" : $ this -> driver = $ this -> createRedisDriver ( ) ; break ; default : throw new SessionException ( "Driver [{$this->config['driver']}] not supported." ) ; } return $ this -> driver ; }
docstring: get session driver
  
  @return \SessionHandlerInterface
  @throws SessionException
docstring_tokens: get session driver