PHP header redirect 301 - what are the implications?

I have domain.com. If the user is logged in, it should load automatically domain.com/option-X where X is a predefined choice of the user.

So, I do this at the top of index.php:

header("Location: /option-X"); 

But, if the user is not logged in, I just choose automatically the first option like this:

header("HTTP/1.1 301 Moved Permanently"); 
header("Location: /option-a"); 

So, i have two questions regarding the implications of doing so:

1. Since the search engines crawlers won't be logged in, they will always get domain.com/option-a - does it affect them that it has a 301 header?
2. What could be the server cpu load of doing those redirects? I don't know how to make a test out of it. The current site (which has no redirects) has about 100k daily visits.

The effect of the 301 would be that the search engines will index /option-a instead of /option-x. Which is probably a good thing since /option-x is not reachable for the search index and thus could have a positive effect on the index. Only if you use this wisely ;-)

After the redirect put exit(); to stop the rest of the script to execute

header("HTTP/1.1 301 Moved Permanently"); 
header("Location: /option-a"); 
exit();

This is better:

<?php
//* Permanently redirect page
header("Location: new_page.php",TRUE,301);
?>

Just one call including code 301. Also notice the relative path to the file in the same directory (not "/dir/dir/new_page.php", etc.), which all modern browsers seem to support.

I think this is valid since PHP 5.1.2, possibly earlier.

Just a tip: using http_response_code is much easier to remember than writing the full header:

http_response_code(301);
header('Location: /option-a'); 
exit;

Make sure you die() after your redirection, and make sure you do your redirect AS SOON AS POSSIBLE while your script executes. It makes sure that no more database queries (if some) are not wasted for nothing. That's the one tip I can give you

For search engines, 301 is the best response code