Hardening further mysql with sqlmap suggestion
There isn't much you can do to "improvise", you need to fix the issue at hand: you're vulnerable to SQL injections.

The most straightforward solution to this is to implement parameterized queries in your code. This will involve changing all the queries manually, but will protect you.

You can read up on it from the article What's the Right Way to Prevent SQL Injection in PHP, but here's an excerpt from the article:


  For example, consider the following login script:
  
  $sql = "SELECT * FROM UserTbl WHERE Username = '$username' and Password = '$password'";
  
  Let’s use the same script, but I’ll define the SQL query with parameter placeholders:
  
  $sql = "SELECT * FROM UserTbl WHERE Username = ? and Password = ?";
  
  Now, I’ll define an array that holds the parameter values:
  
  $params = array($_POST['Username’], $_POST['Password’]);
  
  When I execute the query, I pass the $params array as an argument:
  
  $stmt = sqlsrv_query($conn, $sql, $params);