erro variavel

<?php// db settings are in config.inc// Establish a database connection.$c = dbi_connect ( $db_host, $db_login, $db_password, $db_database );if ( ! $c ) { echo "Error connecting to database:<BLOCKQUOTE>" . dbi_error () . "</BLOCKQUOTE>\n"; exit;}if ( empty ( $login ) && $use_http_auth ) { if ( strstr ( $PHP_SELF, "login.php" ) >= 0 ) { // ignore since login.php will redirect to index.php } else { send_http_login (); }} else if ( ! empty ( $login ) ) { if ( strstr ( $PHP_SELF, "login.php" ) ) { // ignore since login.php will redirect to index.php } else { user_load_variables ( $login, "login_" );--------------------------------------------------------------------------Poque o PHP esta dando erro na variavel PHP_SELF da linha 20?