注意本程序使用的表结构为:
    use test;
    create table image(
                       id int unsigned auto_increment primary key,
                       description text,
                       filename varchar(50),
                       filesize int,
                       filetype varchar(50),
                       filedata longblob
                      );
*/

//?cmd={read|list|form|store}

//检查cmd参数的合法性
switch($cmd){
   case 'read':
      break;
   case 'list':
      break;
   case 'form':
      break;
   Case 'store':
      break;
   default:
      $cmd = 'list';
      break;
}

switch($cmd){
   case 'read':
      //?cmd=read&id={}
      //读一个图片
      $server = mysql_connect("localhost","test","") or die("无法连接数据库服务器");
      mysql_select_db("test",$server) or die("无法连接数据库");
      $sql = "select filetype,filedata from image where id='$id'";
      $rst = mysql_query($sql,$server) or die("$sql查询出错");
      if($row=mysql_fetch_row($rst)){
         header("Content-Type:" . $row[0]);
         echo $row[1];
      }
      else{
         echo "没有找到该记录";
      }
      mysql_free_result($rst);
      mysql_close($server) or die("无法与数据库服务器断开连接");