function str_url($a, $b) {
     return substr($a, 0, strpos($a, $b));
    }

    function self_url() {
    if(!isset($_SERVER['REQUEST_URI'])) {
        $self = $_SERVER['PHP_SELF'];
    }else{
    $self = $_SERVER['REQUEST_URI'];
    }
    $secure = empty($_SERVER["HTTPS"]) ? '' : ($_SERVER["HTTPS"] == "on") ? "s":"";
    $protocol_secure = str_url(strtolower($_SERVER["SERVER_PROTOCOL"]), "/").$secure;
    $port = ($_SERVER["SERVER_PORT"] == "80") ? "" : (":".$_SERVER["SERVER_PORT"]);
    $_SESSION['previous'] = $protocol_secure."://".$_SERVER['SERVER_NAME'].$port.$self;

    header("Location: " . $_SESSION['previous']);
    }