使用PHP在MySQL INSERT QUERY中检查变量存在的简明方法

Question

I am writing a PHP script to add items to a shopping basket. My shopping basket table has fields for the userid, product id, session id, notes and a few others. Some of the fields can be blank. For example:

if someone isn't signed in, then I will store their session id in the table and, if they sign in, add their userid so I have a permanant way to match the items in the table to the user. If they are, I'll add the userid. When it comes to the INSERT query, can I do something like this:

$add_sql = "INSERT into sessionBasket (userid) VALUES ( '". isset($_SESSION["userid"]) ? $_SESSION["userid"] : "") ."'";

It would save me so much time on variable checking and branching because people could be signed in or not, items could have notes or not, that sort of thing.

Answer 1

Yikes! SQL Injection! you could lose your whole database

You should be looking at prepared statements for your sql insertion.

You need to use the mysqli interface but it goes like this:

$statement = $db_connection->prepare("insert into ... VALUES(?)");
$statement->bind_param("id", $sid);
$statement->execute();

This will prevent sql injection attacks.

At an absolute minimum you should at least escape the string.

$sid = isset($_SESSION[userid]) ? mysql_real_escape_string($_SESSION[userid])) : '';
$add_sql = "insert into ... values($sid)";