This is indeed a very odd error, and you’re at least the second one to report it. It seems as if double backslashes have been replaced with single backslashes in three places in the code you posted. It should read:
// automatically assign base_path and base_url
if($base_path==""||$base_url=="") {
$a = explode("/manager",str_replace("\\","/",dirname($_SERVER["PHP_SELF"])));
if(count($a)>1) array_pop($a);
$url = implode("manager",$a); reset($a);
$a = explode("manager",str_replace("\\","/",dirname(__FILE__)));
if(count($a)>1) array_pop($a);
$pth = implode("manager",$a); unset($a);
$base_url = $url.(substr($url,-1)!="/"? "/":"");
$base_path = $pth.(substr($pth,-1)!="/" && substr($pth,-1)!="\\"? "/":"");
$site_url = (!isset($_SERVER['HTTPS']) || strtolower($_SERVER['HTTPS']) != 'on')? 'http://' : 'https://';
$site_url .= $_SERVER['HTTP_HOST'];
if($_SERVER['SERVER_PORT']!=80) $site_url = str_replace(':'.$_SERVER['SERVER_PORT'],'',$site_url); // remove port from HTTP_HOST
$site_url .= ($_SERVER['SERVER_PORT']==80 || isset($_SERVER['HTTPS']) || strtolower($_SERVER['HTTPS'])=='on')? '':':'.$_SERVER['SERVER_PORT'];
$site_url .= $base_url;
}
And of course your database configs should be above that, and the cms session function call below it (this is from a 0.9.6 config file)...
If you change this code can you login normally again?