用session 做一个简单的购物车,我的思想如下, 
1 通过点击连接进行传递商品代号$id,
2 读取txt文件中产品信息,将每条信息写入到一个数组里面 
3 然后将,$id 与数组中每条信息的id对比,找到相应数据, 取出产品 id 与 price 
4 将 id 与price 存入数组$shoppingcart[0]["code"]与 $shoppingcart[0]["price"]中, 然后由数组读出,显示购物信息, 
5 下次 点击传入另一个$id 找到对应的 id 与price, 存入数组第二个 index中($shoppingcart[1]["code"]与 $shoppingcart[1]["price"])中,  然后运算现实价格,总价格等购物信息! 遇到问题:做到第四步的时候没有问题,但是,一个新的$id传进来的时候, 原来存入数组的数据就没了,不知道为什么, 请哪位朋友教教我! 我的代码如下:我这里设置数组的index为session变量,用来保证,每次存取的时候,存到下一个index中去 。  <?php                  <?php session_start();?>
                              if(! isset($_SESSION['user']) )
                               echo "you are not login, please login or register user";  
                           else  
                               {  
                                       $user=$_SESSION['user']; 
                                    $id=$_GET['id'];              
                                  $lines = file("singleproduct.txt");               $count=0;
              foreach ($lines as $line_num => $line) {
              $count=$count+1;
              $new=preg_split("/;/", $line);

             $total[$count] = array(    
                                             code  => $new[0],
                             img   => $new[1],
                             price    => $new[2],
                                            country   =>$new[3],
                                                       descript   =>$new[4],
                                                      );
                                
                                 if($id==$total[$count]["code"])
                                        {   $code=$id; 
                                                  $price=$total[$count]["price"];
                                                  break;
                                                 }
                                                 
                   } 
                                                
                                             
                                               
                                           if(! isset($_SESSION['number']) )
                                           {
                                                 session_register("number"); 
                                                 $_SESSION['number']=0; }
                                              
                                                $secc=$_SESSION['number']; 
                                                                                                      
                                                   $shopping[$secc]=array(
                                                      code => $id,   
                                                               
                                                      price => $price,
                                              );  
                                                      echo "this is test for secc".$secc."this is test for secc<br />";                                                      echo "this is test for code id".$shopping[$secc] ["code"]."this is test for code id<br />";
                                                      echo "this is test for price".$shopping[$_SESSION['number']] ["price"]."this is test for price<br />";                                              echo $shopping[$_SESSION['number']] ["code"];
                                              echo $_SESSION['number'];
                                              echo "<h2>Hello&nbsp;".$user."&nbspyour selected list</h2><br /><br /> ";
                                               
                                             for($i=0;$i<$_SESSION['number'];$i++){
                                                    $testcode= $shopping[$i]["code"];
                                                     $testprice= $shopping[$i]["price"];
                                                 echo $testcode."this is special test";         // 问题就在这里过不去,当新的$id传过来的时候, 只重复当前$id的code 跟price, 上次的没有
                                                            echo $testprice."this is special test";    //这里每次都是 重复显示新传进来$id,对应的值。                                                                }
                                                   $_SESSION['number']++;
                                                echo  $_SESSION['number'];
      
                                                                   }        
                                         
                                                  ?>