如何讓購物車不重複項目？

Question

我需要知道如何不使項目重複，並將數量從showitem.php到數量
但我在sql中更新了表，但是沒有任何事發生在表中，我不知道爲什麼？

這是addtocart.php

<?php 
session_start(); 
function addtocart($id,$qty){ 
if (isset($id)){ 
    //connect to database 
    $mysqli = mysqli_connect("localhost", "root", "", "e-com"); 
    //create safe values for use 
    $safe_sel_item_id = mysqli_real_escape_string($mysqli, 
      $id); 
      $safe_sel_item_qty = mysqli_real_escape_string($mysqli,$qty); 
      //validate item and get title and price 
      $get_iteminfo_sql = "SELECT itemname FROM items WHERE itemid = '".$safe_sel_item_id."'"; 
      $get_iteminfo_res = mysqli_query($mysqli, $get_iteminfo_sql) 
      or die(mysqli_error($mysqli)); 

      if (mysqli_num_rows($get_iteminfo_res) < 1) { 

       //free result 
       mysqli_free_result($get_iteminfo_res); 

       //close connection to MySQL 
       mysqli_close($mysqli); 

       //invalid id, send away 
       header("Location: seestore.php"); 
       exit; 
      } else { 
       //get info 
       while ($item_info = mysqli_fetch_array($get_iteminfo_res)) { 
        $item_title = stripslashes($item_info['itemname']); 
       } 

       //free result 
       mysqli_free_result($get_iteminfo_res); 
       $sql = "select sel_item_qty from shooppertrack where sel_item_id = '" . 
         $safe_sel_item_id . "'"; 

       $res = mysqli_query($mysqli, $sql); 
       while ($res_info = mysqli_fetch_array($get_iteminfo_res)){ 
        $update_qty = $res['sel_item_qty']; 
       } 
       // does quantity exist? 
       if (mysqli_num_rows($res) > 0) { 
        // get sel_item_qty, add 1, run update query 
       "UPDATE shooppertrack SET sel_item_qty = sel_item_qty + $update_qty 
       WHERE sel_item_id = '" .$safe_sel_item_id . "'" ; 
       } else { 
       //add info to cart table 
       $addtocart_sql = "INSERT INTO shooppertrack 
       (session_id, sel_item_id, sel_item_qty, 
         date_added) 
    VALUES ('".$_COOKIE['PHPSESSID']."', 
    '".$safe_sel_item_id."', 
    '".$safe_sel_item_qty."', 
    now())"; 
    $addtocart_res = mysqli_query($mysqli, $addtocart_sql) 
    or die(mysqli_error($mysqli)); 
       }     
    //close connection to MySQL 
    mysqli_close($mysqli); 
    //redirect to showcart page 
    header("Location: showcart.php"); 
    exit; 
      } 
} else { 
    //send them somewhere else 
    header("Location: seestore.php"); 
    exit; 
} 
} 
addtocart($_POST['sel_item_id'],$_POST['sel_item_qty']); 
?> 

這是showitem.php即可

<?php 
    function show($x){ 
     //connect to database 
    $mysqli = mysqli_connect("localhost", "root", "", "e-com"); 
    $display_block = "<h1>My Store - Item Detail</h1>"; 

    //create safe values for use 
    $safe_item_id = mysqli_real_escape_string($mysqli, $x); 

    //validate item 
    $get_item_sql = "SELECT c.cat_id , c.cat_name, si.itemid, si.itemname, 
    si.price, si.descripition, si.photo FROM items 
    AS si LEFT JOIN categories AS c on c.cat_id = si.cat_id 
    WHERE si.itemid = '".$safe_item_id."'"; 
$get_item_res = mysqli_query($mysqli, $get_item_sql) 
or die(mysqli_error($mysqli)); 

if (mysqli_num_rows($get_item_res) < 1) { 
//invalid item 
$display_block .= "<p><em>Invalid item selection.</em></p>"; 
} else { 
//valid item, get info 
    while ($item_info = mysqli_fetch_array($get_item_res)) { 
     $cat_id = $item_info['cat_id']; 
     $cat_title = strtoupper(stripslashes($item_info['cat_name'])); 
     $item_title = stripslashes($item_info['itemname']); 
     $item_price = $item_info['price']; 
     $item_desc = stripslashes($item_info['descripition']); 
     $item_image = $item_info['photo']; 
    } 

    //make breadcrumb trail & display of item 
    $display_block .= <<<END_OF_TEXT 
    <p><em>You are viewing:</em><br/> 
    <strong><a href="seestore.php?cat_id=$cat_id">$cat_title</a> &gt; $item_title</strong></p> 
    <div style="float: left;"><img src="$item_image" alt="$item_title" /></div> 
    <div style="float: left; padding-left: 12px"> 
    <p><strong>Description:</strong><br/>$item_desc</p> 
    <p><strong>Price:</strong> \$$item_price</p> 
<form method="POST" action="addtocart.php"> 
END_OF_TEXT; 
//free result 
mysqli_free_result($get_item_res); 

    $display_block .= " 
    <p><label for=\"sel_item_qty\">Select Quantity:</label> 
    <select id=\"sel_item_qty\" name=\"sel_item_qty\">"; 

    for($i=1; $i<11; $i++) { 
    $display_block .= "<option value=\"".$i."\">".$i."</option>"; 
    } 
    $display_block .=<<<ENDOFTEXT 
    </select><p> 
     <input type="hidden" name="sel_item_id" value="$_GET[itemid]" /> 
    <button type="submit" name="submit" value="submit">Add to Cart</button> 
    </form> 
    </div> 
ENDOFTEXT; 
} 
return $display_block; 
    //close connection to MySQL 
    mysqli_close($mysqli); 
    } 
    ?> 

Answer 1

您需要在插入前查詢您的購物車中的物品和會話。如果存在，則應該更新數量。

$sql = 'select sel_item_qty from shooppertrack where sel_item_id = ' . 
     $safe_sel_item_id . ' and session_id = ' $_COOKIE['PHPSESSID']; 

$res = mysqli_query($mysqli, $sql); 

// does quantity exist? 
if (mysqli_num_rows($res) > 0) { 
    // get sel_item_qty, add 1, run update query 
} else { 
    // run your insert query 
} 

Answer 2

試試這個
//添加信息到購物車表

$sql = "Select session_id, sel_item_id from shooppertrack where session_id = $sid and sel_item_id = $si_id"; 

$res = mysqli_query($mysqli, $sql); 

if(mysqli_num_rows($res) == 1) 
{ 
// update with qty +1; 
}else{ 
$addtocart_sql = "INSERT INTO shooppertrack 
       (session_id, sel_item_id, sel_item_qty, 
         date_added) 
       VALUES ('".$_COOKIE['PHPSESSID']."', 
       '".$safe_sel_item_id."', 
       '".$safe_sel_item_qty."', 
       now())"; 
       $addtocart_res = mysqli_query($mysqli, $addtocart_sql) 
       or die(mysqli_error($mysqli)); 
}