Wordpress relative URL

// Use wp-config-local.php for local server settings, don't check that file onto the server
if ( file_exists( dirname( __FILE__ ) . '/wp-config-local.php' ) ) {
	include( dirname( __FILE__ ) . '/wp-config-local.php' );

	// Otherwise use the below settings (on live server)
} else {

	// Live Server Database Settings
	define( 'DB_NAME',     'db_name');
	define( 'DB_USER',     'db_username');
	define( 'DB_PASSWORD', 'db_password' );
	define( 'DB_HOST',     'localhost'  );

	define('WP_SITEURL', 'http://' . $_SERVER['HTTP_HOST']);
	define('WP_HOME', 'http://' . $_SERVER['HTTP_HOST']);

	// Turn Debug off on live server
	define('WP_DEBUG', false);
}