title: PHP - GetSQLValueString function
body: <p>I see a function GetSQLValueString and I don't know what is it dealing with, could someone give me some idea?<br />
  Thanks you</p>
  
  <pre><code>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;
  }
  </code></pre>
  
  <p>The function used here:</p>
  
  <pre><code>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")); 
  ...
  </code></pre>