比较模糊的是session_decode和session_encode:  bool session_decode(string data);  session_decode() decodes the session data in data, setting variables  stored in the session.  bool session_encode(void);  session_encode() returns a string with the contents of the current  sessionencoded within.  php manual里面好象没有相关的例子。从字面意思来看decode是把用户的串  解析出来以后set到session里面,encode则是把session的数据“打包”返回  给用户。这样看来encode的作用可能更大一些,用户register数据到session  里面以后应该是用encode把数据取出来的,但是encode返回的东西仍需要处理,  比如:  session_register("val1");  $val1 = "abcde"  session_register("val2");  $val1 = 1234  session_register("val3");  $val1 = 123.45  那么session_encode返回的东西是:  val1:s:5:"abcde";val2:i:1234;val3:d:123.45;  很明显,"s"是string,"i"和"d"是数字,"s"类型的变量需要长度。  如果你的session id是aaeebbcfd4455ec2c0d5cb590f8fab74,那么这串东西实际  上是存在/tmp/aaeebbcfd4455ec2c0d5cb590f8fab74文件当中。  现在需要你自己把这串东西做处理,析出你想要的session data。很奇怪php4  没提供一个方便的接口实现已register变量的解析... 或者有我没找着。  先自己写一个了...  session_data_init取出所有“打包”的session_data  session_data_get根据变量名取得数据  用:  $data = session_data_init( );  $result = session_data_get($data, "val1");  就可以把val1的数据取出来。  <?  /*  * get all date registered in the session  */  function session_data_init( ) {      $sessionData = session_encode();      return $sessionData;  }  ?>  <?  /*  * extract one variable from enconded session data  */  function session_data_get($data, $name) {      $matchStr = $name."|";      $matchStart = strpos($data, $matchStr);      if ($matchStart == 0) {          if (strlen($data) < strlen($matchStr)) return "";          $tmpStr = substr($data, 0, strlen($matchStr));          if (strcmp($tmpStr, $matchStr) != 0) return "";      }      $typeStart = $matchStart + strlen($matchStr);      $dataType = substr($data, $typeStart, 1);      if (strcmp($dataType, "s") == 0) {   /* string */          $lenStart = $typeStart + 2;          $lenEnd = strpos($data, ":", $lenStart) - 1;          $lenLen = $lenEnd - $lenStart + 1;          $strLen = substr($data, $lenStart, $lenLen);          $strStart = $lenEnd + 3;          $strResult = substr($data, $strStart, $strLen);          return $strResult;      } else if (strcmp($dataType, "i") == 0 ||          strcmp($dataType, "d") == 0) { /* number */          $numStart = $typeStart + 2;          $numEnd = strpos($data, ";", $numStart) - 1;          $numLen = numEnd - numStart + 1;          $numResult = substr($data, $numStart, $numLen);         return $numResult;     } else {         return "";     } } ?>