Not Able To Show Message After Logedout

Question

i've done the functionality of when user is logged in from one device. then if he logged in from other device then he'll be logedout and redirect to login page.

 

i've done this functionality through a session. when user logged in I save a value in database and every time he go to other page i match the values (saved in database and in session both) if they dont match (if user is logged in from other device the value in database will be updated so will not match with the session value ) i redirect user to login page 

 

the problem is i'm not able to show message (simple message or popup ) when user go to loggin page. 

 

kindly tell me how can i show message ?

 

or tell me if this functionality i've done is not good or i've to use some other method through javascript or any other resource