CSS in javascript-php

Recently, I encountered the problem of introducing css when using php. I added a login in the Header bar of the page and used session to check the user's status. LoginFilter. php {code ...} this method is used to check whether a user has logged on. if the user has logged on, the personal center is displayed... recently, I encountered the problem of introducing css when using php. I added a login in the Header bar of the page and used session to check the user's status.

LoginFilter. php

  Login"; Echo"
Register
";} Else {echo"
Personal Center
";}?>

This method is used to check whether a user has logged on. if the user has logged on, the personal center is displayed. Otherwise, the logon and registration are displayed.
In the UI library, I used the font-awsome UI library, but found that I elements cannot be used, such

Echo"
Personal Center
";

Finally inserted into the ul of the Header

  
  
 
   
 
   
 Home
 
   
 League
 
   
 Players
 
   
 Team
  
  

Later, I used the Bootstrap UI library, but it still didn't work. so I think it may be the problem of introducing css format errors in php.

How can I introduce css into it?

Reply content:

Recently, I encountered the problem of introducing css when using php. I added a login in the Header bar of the page and used session to check the user's status.

LoginFilter. php

  Login"; Echo"
Register
";} Else {echo"
Personal Center
";}?>

This method is used to check whether a user has logged on. if the user has logged on, the personal center is displayed. Otherwise, the logon and registration are displayed.
In the UI library, I used the font-awsome UI library, but found that I elements cannot be used, such

Echo"
Personal Center
";

Finally inserted into the ul of the Header

  
  
 
   
 
   
 Home
 
   
 League
 
   
 Players
 
   
 Team
  
  

Later, I used the Bootstrap UI library, but it still didn't work. so I think it may be the problem of introducing css format errors in php.

How can I introduce css into it?

Determine that the login should be controlled in the controller, and then render different view views based on the judgment results. Too many business logic judgments should not be made in the view.
In addition, your code is incorrect. the correct code:

Echo'
Personal Center
';

Without figuring out what the problem is, you can directly add it to the html head tag.

It is introduced. what do you mean when I elements cannot be used? is it not displayed or style.