+define('_URL_SCHEME_COLON_DOUBLE_SLASH', 1);
+define('_URL_SCHEME_SINGLE_COLON', 2);
+define('_URL_SCHEME_NO_DOMAIN', 4);
+define('_URL_SCHEME_COLON_COORDINATES', 8);
+
+function common_url_schemes($filter=null)
+{
+ // TODO: move these to $config
+ $schemes = [
+ 'http' => _URL_SCHEME_COLON_DOUBLE_SLASH,
+ 'https' => _URL_SCHEME_COLON_DOUBLE_SLASH,
+ 'ftp' => _URL_SCHEME_COLON_DOUBLE_SLASH,
+ 'ftps' => _URL_SCHEME_COLON_DOUBLE_SLASH,
+ 'mms' => _URL_SCHEME_COLON_DOUBLE_SLASH,
+ 'rtsp' => _URL_SCHEME_COLON_DOUBLE_SLASH,
+ 'gopher' => _URL_SCHEME_COLON_DOUBLE_SLASH,
+ 'news' => _URL_SCHEME_COLON_DOUBLE_SLASH,
+ 'nntp' => _URL_SCHEME_COLON_DOUBLE_SLASH,
+ 'telnet' => _URL_SCHEME_COLON_DOUBLE_SLASH,
+ 'wais' => _URL_SCHEME_COLON_DOUBLE_SLASH,
+ 'file' => _URL_SCHEME_COLON_DOUBLE_SLASH,
+ 'prospero' => _URL_SCHEME_COLON_DOUBLE_SLASH,
+ 'webcal' => _URL_SCHEME_COLON_DOUBLE_SLASH,
+ 'irc' => _URL_SCHEME_COLON_DOUBLE_SLASH,
+ 'ircs' => _URL_SCHEME_COLON_DOUBLE_SLASH,
+ 'aim' => _URL_SCHEME_SINGLE_COLON,
+ 'bitcoin' => _URL_SCHEME_SINGLE_COLON,
+ 'fax' => _URL_SCHEME_SINGLE_COLON,
+ 'jabber' => _URL_SCHEME_SINGLE_COLON,
+ 'mailto' => _URL_SCHEME_SINGLE_COLON,
+ 'tel' => _URL_SCHEME_SINGLE_COLON,
+ 'xmpp' => _URL_SCHEME_SINGLE_COLON,
+ 'magnet' => _URL_SCHEME_NO_DOMAIN,
+ 'geo' => _URL_SCHEME_COLON_COORDINATES,
+ ];
+
+ return array_keys(
+ array_filter($schemes,
+ function ($scheme) use ($filter) {
+ return is_null($filter) || ($scheme & $filter);
+ })
+ );
+}
+