PHP Web Application Root URL

I wrote this little function to return a PHP applicaiton's root url. It is very quick and dirty, but I thought I'd still share it:

function get_app_root_url()
{
    $app_root_dir_name = getcwd();
    $idx = strripos($app_root_dir_name, '/');
    
    if($idx >= 0)
        $app_root_dir_name = substr($app_root_dir_name, $idx + 1);

    $app_root_url = get_page_url();
    
    $idx = strpos($app_root_url, $app_root_dir_name);
    
    if($idx >= 0)
        $app_root_url = substr($app_root_url, 0, $idx + strlen($app_root_dir_name));
        
    return $app_root_url;
}

// Curtosy of http://www.webcheatsheet.com/PHP/get_current_page_url.php
function get_page_url() 
{
    $page_url = 'http';
    
    if ($_SERVER["HTTPS"] == "on") 
        $page_url .= "s";
    
    $page_url .= "://";
    
    if ($_SERVER["SERVER_PORT"] != "80") 
        $page_url .= $_SERVER["SERVER_NAME"].":".$_SERVER["SERVER_PORT"].$_SERVER["REQUEST_URI"];
    else 
        $page_url .= $_SERVER["SERVER_NAME"].$_SERVER["REQUEST_URI"];
    
    return $page_url;
}