diff --git a/src/PDOWithFilters/PDOWithFilters.php b/src/PDOWithFilters/PDOWithFilters.php
index dd387ce..beee684 100644
--- a/src/PDOWithFilters/PDOWithFilters.php
+++ b/src/PDOWithFilters/PDOWithFilters.php
@@ -35,16 +35,16 @@ class PDOWithFilters {
 
 
   public static function connect($dsn, $username, $password) {
-    if (!empty($pdo)) {
+    if (!empty(self::$pdo)) {
       throw new \Exception('Create Pdo only once');
     }
-    self::$pdo = new \PDO($dsn, $username, $password);
+    self::$pdo = new \PDO($dsn, $username, $password, [\PDO::ATTR_PERSISTENT => true]);
 
     return self::$pdo;
   }
 
   public static function getPDOInstance() {
-    if (empty($pdo)) {
+    if (empty(self::$pdo)) {
       throw new \Exception('You must call connect() first');
     }
     return self::$pdo;