wp_clear_auth_cookie()

function wp_clear_auth_cookie() {
	/**
	 * Fires just before the authentication cookies are cleared.
	 *
	 * @since WP-2.7.0
	 */
	do_action( 'clear_auth_cookie' );

	/** This filter is documented in wp-includes/pluggable.php */
	if ( ! apply_filters( 'send_auth_cookies', true ) ) {
		return;
	}

	// Auth cookies
	setcookie( AUTH_COOKIE,        ' ', time() - YEAR_IN_SECONDS, ADMIN_COOKIE_PATH,   COOKIE_DOMAIN );
	setcookie( SECURE_AUTH_COOKIE, ' ', time() - YEAR_IN_SECONDS, ADMIN_COOKIE_PATH,   COOKIE_DOMAIN );
	setcookie( AUTH_COOKIE,        ' ', time() - YEAR_IN_SECONDS, PLUGINS_COOKIE_PATH, COOKIE_DOMAIN );
	setcookie( SECURE_AUTH_COOKIE, ' ', time() - YEAR_IN_SECONDS, PLUGINS_COOKIE_PATH, COOKIE_DOMAIN );
	setcookie( LOGGED_IN_COOKIE,   ' ', time() - YEAR_IN_SECONDS, COOKIEPATH,          COOKIE_DOMAIN );
	setcookie( LOGGED_IN_COOKIE,   ' ', time() - YEAR_IN_SECONDS, SITECOOKIEPATH,      COOKIE_DOMAIN );

	// Settings cookies
	setcookie( 'wp-settings-' . get_current_user_id(),      ' ', time() - YEAR_IN_SECONDS, SITECOOKIEPATH );
	setcookie( 'wp-settings-time-' . get_current_user_id(), ' ', time() - YEAR_IN_SECONDS, SITECOOKIEPATH );

	// Old cookies
	setcookie( AUTH_COOKIE,        ' ', time() - YEAR_IN_SECONDS, COOKIEPATH,     COOKIE_DOMAIN );
	setcookie( AUTH_COOKIE,        ' ', time() - YEAR_IN_SECONDS, SITECOOKIEPATH, COOKIE_DOMAIN );
	setcookie( SECURE_AUTH_COOKIE, ' ', time() - YEAR_IN_SECONDS, COOKIEPATH,     COOKIE_DOMAIN );
	setcookie( SECURE_AUTH_COOKIE, ' ', time() - YEAR_IN_SECONDS, SITECOOKIEPATH, COOKIE_DOMAIN );

	// Even older cookies
	setcookie( USER_COOKIE, ' ', time() - YEAR_IN_SECONDS, COOKIEPATH,     COOKIE_DOMAIN );
	setcookie( PASS_COOKIE, ' ', time() - YEAR_IN_SECONDS, COOKIEPATH,     COOKIE_DOMAIN );
	setcookie( USER_COOKIE, ' ', time() - YEAR_IN_SECONDS, SITECOOKIEPATH, COOKIE_DOMAIN );
	setcookie( PASS_COOKIE, ' ', time() - YEAR_IN_SECONDS, SITECOOKIEPATH, COOKIE_DOMAIN );

	// Post password cookie
	setcookie( 'wp-postpass_' . COOKIEHASH, ' ', time() - YEAR_IN_SECONDS, COOKIEPATH, COOKIE_DOMAIN );
}