the limesurvey installer generates a config.php file in which the 'session' part is as follows:
'session' => array (
'sessionName'=>'LS-CDAGLJWFNFAVEZJU'
// Uncomment the following lines if you need table-based sessions.
// Note: Table-based sessions are currently not supported on MSSQL server.
// 'class' => 'application.core.web.DbHttpSession',
// 'connectionID' => 'db',
// 'sessionTableName' => '{{sessions}}',
),

If you just uncomment the lines as stated, you get wrong positioning for commas, like this:
'session' => array (
'sessionName'=>'LS-CDAGLJWFNFAVEZJU' <----- missing comma
// Uncomment the following lines if you need table-based sessions.
// Note: Table-based sessions are currently not supported on MSSQL server.
'class' => 'application.core.web.DbHttpSession',
'connectionID' => 'db',
'sessionTableName' => '{{sessions}}',
),