如何防止重复记录插入购物车 (PHP)

Question

我目前正在研究购物车。我想防止它在购物车上有重复的项目。例如：如果我点击"熊猫"，购物车中的数量将是1。如果我再次点击"熊猫"，数量将变为 2 ，而不是购物车中有 2 个"熊猫"项目。有人可以指导我吗？我是PHP的新手，您的帮助将不胜感激。谢谢

这是我的代码。

详情.php

   if ((isset($_POST["MM_insert"])) && ($_POST["MM_insert"] == "form1")) {
$status = $this->checkProductStatus($yourdata)
if ($status){
// write your update query
$updateSQL = sprintf("UPDATE supermarketcart SET qty=%s WHERE id=%s",
                       GetSQLValueString($_POST['name'], "text"),
                       GetSQLValueString($_POST['description'], "text"),
                       GetSQLValueString($_POST['package'], "text"),
                       GetSQLValueString($_POST['price'], "double"),
                       GetSQLValueString($_POST['imagename'], "text"),
                       GetSQLValueString($_POST['username'], "text"));
}
else{
//write your insert query
  $insertSQL = sprintf("INSERT INTO supermarketcart (pname, pdescription, package, pprice, pimage, username) VALUES (%s, %s, %s, %s, %s, %s)",
                       GetSQLValueString($_POST['name'], "text"),
                       GetSQLValueString($_POST['description'], "text"),
                       GetSQLValueString($_POST['package'], "text"),
                       GetSQLValueString($_POST['price'], "double"),
                       GetSQLValueString($_POST['imagename'], "text"),
                       GetSQLValueString($_POST['username'], "text"));
  mysql_select_db($database_MyDatabase, $MyDatabase);
  $Result1 = mysql_query($insertSQL, $MyDatabase) or die(mysql_error());
  $insertGoTo = "cart.php";
  if (isset($_SERVER['QUERY_STRING'])) {
    $insertGoTo .= (strpos($insertGoTo, '?')) ? "&" : "?";
    $insertGoTo .= $_SERVER['QUERY_STRING'];
  }
  header(sprintf("Location: %s", $insertGoTo));
}
$colname_supermarketDetails = "-1";
if (isset($_GET['desc_sel'])) {
  $colname_supermarketDetails = $_GET['desc_sel'];
}
mysql_select_db($database_MyDatabase, $MyDatabase);
$query_supermarketDetails = sprintf("SELECT * FROM supermarket WHERE `description` = %s", GetSQLValueString($colname_supermarketDetails, "text"));
$supermarketDetails = mysql_query($query_supermarketDetails, $MyDatabase) or die(mysql_error());
$row_supermarketDetails = mysql_fetch_assoc($supermarketDetails);
$totalRows_supermarketDetails = mysql_num_rows($supermarketDetails);
mysql_select_db($database_MyDatabase, $MyDatabase);
$query_cart = "SELECT * FROM supermarketcart";
$cart = mysql_query($query_cart, $MyDatabase) or die(mysql_error());
$row_cart = mysql_fetch_assoc($cart);
$totalRows_cart = mysql_num_rows($cart);
$colname_supermarketInfo = "-1";
if (isset($_GET['id'])) {
  $colname_supermarketInfo = $_GET['id'];


}
mysql_select_db($database_MyDatabase, $MyDatabase);
$query_supermarketInfo = sprintf("SELECT * FROM supermarket WHERE `description` = %s", GetSQLValueString($colname_supermarketInfo, "text"));
$supermarketInfo = mysql_query($query_supermarketInfo, $MyDatabase) or die(mysql_error());
$row_supermarketInfo = mysql_fetch_assoc($supermarketInfo);
}
public function checkProductStatus($data){
// check the if the product already exist against that user
return true 
else false
}

Answer 1

if ((isset($_POST["MM_insert"])) && ($_POST["MM_insert"] == "form1")){
$status = $this->checkProductStatus($yourdata)
if ($status){
// write your update query
}
else{
//write your insert query
}
}
public function checkProductStatus($data){
// check the if the product already exist against that user
return true else false
}