Run a css depending on the current logged in username

This script will add custom css on our wordpress backend if the current logged in user name is "guest".

$current_user = wp_get_current_user();
if ( $current_user->user_login == "guest" ) {
 add_action('admin_head', 'hideMenus');
 function hideMenus() {
   echo '<style>
   #menu-media,#menu-comments,#menu-users,#menu-posts{
    display:none !important;
   }    
    </style>';
 } 
}