带有$ var数据的SQL Update列

Question

$newCity = $_POST['city'];

$set = mysqli_query($con, "UPDATE users SET city = '$newCity' WHERE username = '$theUser'");

我正在尝试使用变量值更新mySql列到UPDATE。 但是当我检查该值时，它会更新，但是一旦我刷新执行，它就会将值更改为NULL

修改：$theUser = a working session username

Answer 1

尝试：

if(isset($_POST['city'])){
 $newCity = $_POST['city'];
 $set = mysqli_query($con, "UPDATE users SET city = '$newCity' WHERE username = '$theUser'");
}

另外，请在将用户输入传递给查询之前尝试过滤。

Answer 2

if(isset($_POST['city'])){
   $newCity = mysqli_real_escape_string($_POST['city']);
   $theUser = mysqli_real_escape_string($userUser); // assuming you haven't escaped it already.
   $query = "UPDATE users SET city = '$newCity' WHERE username = '$theUser'";
   $set = mysqli_query($con, $query);
}