in php please using simple if statement for the last step and if possible explain it , thank you

Exercise 2 (Website) - Create a page called log_in.php - The page will contain a form with the following fields: - UserName (username field) - password (password field) - The form method is POST - The page that will handle the data is called handle_log_in.php - handle_log in.php will check if the username is equal to "test_username" and the password is test_pass. If the email and password are correct then print to the user "Welcome back". If either of the email or password is wrong then print "The Username Or Password is not correct