当用户登录时，如何让登录按钮更改为图标？

On my home page, in the header, I have a login button that opens a modal & successfully allows users to sign in but once a user is logged in I want the existing login button to change to an glyph-icon & remain a glyph-icon unless the user logs out . How can that be done? P.S. I'm using Wordpress, Woocommerce & Twitter Bootstrap.On my home page, in the header, I have a login