Jommla 3.5.1 Session Conflict - Duplicate session headers have already been sent

Question

I have recently upgraded to Joomla 3.5.1 and I get the following error when I load/include a php file on my root directory.

"Error displaying the error page: Application Instantiation Error: Failed to start the session because headers have already been sent by test.php at line 1"

I am loading test.php file in a module. The test.php is on the main root of joomla installation. However, since Joomla itself has already sets the session, I can't access joomla database thru test.php because of the session error above.

In the test.php, I have the following code to start with;

<?php

define( '_JEXEC', 1 );
define( '_VALID_MOS', 1 );
define( 'JPATH_BASE', realpath(dirname(__FILE__)));
define( 'DS', DIRECTORY_SEPARATOR );
require_once ( JPATH_BASE .DS.'includes'.DS.'defines.php' );
require_once ( JPATH_BASE .DS.'includes'.DS.'framework.php' );


$mainframe = JFactory::getApplication('site');
$mainframe->initialise();

It was working just fine before the upgrade. How can I prevent the session conflict in Joomla when I load external php file to access joomla database?

Answer 1

Typically this issue is caused by an almost unnoticeable space (or new line) at the beginning of the file. Check your test.php file for any spaces before the opening <?php .

Answer 2

I think the reason why you get this error after the 3.5.1 update is that they now throw an exception in /libraries/joomla/session/handler/native.php line 252 if header_sent() returns true. To avoid that you can try to set the "session.use_cookies" directive to false with

ini_set('session.use_cookies', 0);

But that is really more a trick than a solution you shouldn't do that. In fact I can't think of any reason why you want to reinitialize the Joomla! framework like that. The proper way is to create a file like /modules/mod_mymod/helper.php

 defined('_JEXEC') or die('Restricted access');

 class MyModHelper {
    public static function doSth() {
        $db = JFactory::getDBO();
        //your code here
    }
 }

And then you can execute the code from almost anywhere with

require_once JPATH_ROOT.DIRECTORY_SEPARATOR.'modules'.DIRECTORY_SEPARATOR.'mod_mymod'.DIRECTORY_SEPARATOR.'helper.php';
MyModHelper::doSth();

But I came here because I got the same error on executing a Joomla! CLI script. So just a few words to this because your heading fits somehow. On some machines the header_sent() method seems to return true even for the default Joomla! CLI scripts like "finder_indexer.php". To solve this I wrote

ob_start();

at the beginning of the script to buffer the output and prevent any CLI output before the session actually starts.