Revert "Set the session name explicitly in SessionHandlerPHP, even when we are...

Revert "Set the session name explicitly in SessionHandlerPHP, even when we are using the default value."

This reverts commit cd6278cc.

lib/SimpleSAML/SessionHandlerPHP.php

@@ -42,7 +42,7 @@ class SimpleSAML_SessionHandlerPHP extends SimpleSAML_SessionHandler
         parent::__construct();
 
         $config = SimpleSAML_Configuration::getInstance();
-        $this->cookie_name = $config->getString('session.phpsession.cookiename', ini_get('session.name'));
+        $this->cookie_name = $config->getString('session.phpsession.cookiename', null);
 
         if (function_exists('session_status') && defined('PHP_SESSION_ACTIVE')) { // PHP >= 5.4
             $previous_session = session_status() === PHP_SESSION_ACTIVE;
@@ -61,7 +61,11 @@ class SimpleSAML_SessionHandlerPHP extends SimpleSAML_SessionHandler
             session_write_close();
         }
 
-        session_name($this->cookie_name);
+        if (!empty($this->cookie_name)) {
+            session_name($this->cookie_name);
+        } else {
+            $this->cookie_name = session_name();
+        }
 
         $params = $this->getCookieParams();