no page is shown when setting.php file is changed

hi
I'm new here and I have a problem and I wonder if you guys can help me out.
I've changed the setting page as below :

$databases = array (
'default' =>
array (
'default' =>
array (
'database' => 'XXX',
'username' => 'XXX',
'password' => 'XXX',
'host' => 'localhost',
'port' => '',
'driver' => 'mysql',
'prefix' => '',
),
),
);

$databases['ls']['default'] = array(
'driver' => 'mysql',
'database' => 'XXX',
'username' => 'XXX',
'password' => 'XXX',
'host' => 'localhost',
'prefix' => 'lime_' [or another value],
'collation' => 'utf8_general_ci' [or another value],
);

when I refresh the page to see it works or not an empty page is shown and nothing else happens,
what should I do to fix this?