Method getInstance

/**
 * Returns the global Uri object, only creating it if it doesn't already exist.
 *
 * @param   string  $uri  The URI to parse.  [optional: if null uses script URI]
 *
 * @return  Uri  The URI object.
 *
 * @since   1.7.0
 */
public static function getInstance($uri = 'SERVER')
{
    if (empty(static::$instances[$uri])) {
        // Are we obtaining the URI from the server?
        if ($uri === 'SERVER') {
            // Determine if the request was over SSL (HTTPS).
            if (isset($_SERVER['HTTPS']) && !empty($_SERVER['HTTPS']) && strtolower($_SERVER['HTTPS']) !== 'off') {
                $https = 's://';
            } elseif (isset($_SERVER['HTTP_X_FORWARDED_PROTO']) && !empty($_SERVER['HTTP_X_FORWARDED_PROTO']) && strtolower($_SERVER['HTTP_X_FORWARDED_PROTO']) !== 'http') {
                $https = 's://';
            } else {
                $https = '://';
            }
            /*
             * Since we are assigning the URI from the server variables, we first need
             * to determine if we are running on apache or IIS.  If PHP_SELF and REQUEST_URI
             * are present, we will assume we are running on apache.
             */
            if (!empty($_SERVER['PHP_SELF']) && !empty($_SERVER['REQUEST_URI'])) {
                // To build the entire URI we need to prepend the protocol, and the http host
                // to the URI string.
                $theURI = 'http' . $https . $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI'];
            } else {
                /*
                 * Since we do not have REQUEST_URI to work with, we will assume we are
                 * running on IIS and will therefore need to work some magic with the SCRIPT_NAME and
                 * QUERY_STRING environment variables.
                 *
                 * IIS uses the SCRIPT_NAME variable instead of a REQUEST_URI variable... thanks, MS
                 */
                $theURI = 'http' . $https . $_SERVER['HTTP_HOST'] . $_SERVER['SCRIPT_NAME'];
                // If the query string exists append it to the URI string
                if (isset($_SERVER['QUERY_STRING']) && !empty($_SERVER['QUERY_STRING'])) {
                    $theURI .= '?' . $_SERVER['QUERY_STRING'];
                }
            }
            // Extra cleanup to remove invalid chars in the URL to prevent injections through the Host header
            $theURI = str_replace(array("'", '"', '<', '>'), array('%27', '%22', '%3C', '%3E'), $theURI);
        } else {
            // We were given a URI
            $theURI = $uri;
        }
        static::$instances[$uri] = new static($theURI);
    }
    return static::$instances[$uri];
}