我将如何在php mysql中的一个变量中获取2个不同的行？

Question

What am I trying to do is when the customer buys from my cart, the quantity of the product will be subtracted from the quantity the customer buys? I'm expecting multiple products the customer will buy.

Here's my code.

$x=$_SESSION['products'];
        foreach($x as $id => $y){ 
        $insert_row = $mysqli->query("INSERT INTO transaction 
        VALUES (null,'$buyerName','$buyerEmail','$transactionID','$y[code]','$y[qty]',NOW(),'Pending')");
        $result1=mysql_query("SELECT quantity from products where product_code='$y[code]'");
        if(mysql_num_rows($result1)>0){
            $row=mysql_fetch_object($result1);
            $currqty=$row->quantity;
            echo "".$currqty;
        }else{
            echo "No record found";
        }

Answer 1

SELECT GROUP_CONCAT(product) AS res FROM table WHERE foo=1 GROUP BY foo;

that way you will have a list of all products in "res" matching on foo=1, while getting just one row.

find more about group_concat here:

http://dev.mysql.com/doc/refman/5.0/en/group-by-functions.html#function_group-concat

Answer 2

If the purpose of your code is to substract the quantity from products after a successful insert into transaction , here is an optimized version of your code, that achieves this:

foreach($_SESSION['products'] as $id => $y) {
    $insert_row = $mysqli->query("
        INSERT INTO transaction
        VALUES (null,'$buyerName','$buyerEmail','$transactionID','$y[code]','$y[qty]',NOW(),'Pending')"
    );
    if($insert_row) {
        ## Important: substract the quantity from products only if a successful 
        ##            insert has been made in the transaction table
        $result1 = mysql_query("UPDATE products SET quantity = quantity - {$y[qty]} WHERE product_code='$y[code]'");
        if($result1) {
            echo "quantity updated";
        }
    }
}