function GetSQLValueString($theValue, $theType, $theDefinedValue = "", $theNotDefinedValue = "")
{
  $theValue = get_magic_quotes_gpc() ? stripslashes($theValue) : $theValue;

  $theValue = function_exists("mysql_real_escape_string") ? mysql_real_escape_string($theValue) : mysql_escape_string($theValue);

  switch ($theType) {
    case "text":
      $theValue = ($theValue != "") ? "'" . $theValue . "'" : "NULL";
      break;
    case "long":
    case "int":
      $theValue = ($theValue != "") ? intval($theValue) : "NULL";
      break;
    case "double":
      $theValue = ($theValue != "") ? "'" . doubleval($theValue) . "'" : "NULL";
      break;
    case "date":
      $theValue = ($theValue != "") ? "'" . $theValue . "'" : "NULL";
      break;
    case "defined":
      $theValue = ($theValue != "") ? $theDefinedValue : $theNotDefinedValue;
      break;
  }
  return $theValue;
}

if (isset($_POST['username'])) {
  $loginUsername=$_POST['username'];
  $password=$_POST['password'];
  $MM_fldUserAuthorization = "";
  $MM_redirectLoginSuccess = "main.php";
  $MM_redirectLoginFailed = "login_form.php";
  $MM_redirecttoReferrer = false;
  mysql_select_db($database_connection1, $connection1);

  $LoginRS__query=sprintf("SELECT username, password FROM member WHERE username=%s AND password=%s",
    GetSQLValueString($loginUsername, "text"), GetSQLValueString($password, "text"));
...

$sql = "SELECT * FROM users WHERE username = " . GetSQLValueString($_GET['username'], 'text');
$result = mysql_query($sql);

GetSQLValueString("a value that I want to escape's", 'text');

function GetSQLValueString($conn_vote, $theValue, $theType, $theDefinedValue = "", $theNotDefinedValue = "")
    {
      $theValue = get_magic_quotes_gpc() ? stripslashes($theValue) : $theValue;

      $theValue = function_exists("mysqli_real_escape_string") ? mysqli_real_escape_string($conn_vote, $theValue) : mysqli_escape_string($conn_vote, $theValue);`enter code here`

      switch ($theType) {
        case "text":
          $theValue = ($theValue != "") ? "'" . $theValue . "'" : "NULL";
          break;
        case "long":
        case "int":
          $theValue = ($theValue != "") ? intval($theValue) : "NULL";
          break;
        case "double":
          $theValue = ($theValue != "") ? "'" . doubleval($theValue) . "'" : "NULL";
          break;
        case "date":
          $theValue = ($theValue != "") ? "'" . $theValue . "'" : "NULL";
          break;
        case "defined":
          $theValue = ($theValue != "") ? $theDefinedValue : $theNotDefinedValue;
          break;
      }
      return $theValue;
    }
    }