PHP redirect and link juice?

how does a php redirect work in terms of link juice flow?

like if i have a traffic exchange and i send traffic by doing:

www.mysite.com/out.php?exchange=www.othersite.com

what are the positives and negatives of doing it this way?

 

Google will pass PR to destination URL via 301 redirect

 

but it is not a 301 redirect. i just use the php file to link to another site.

 

This kind of redirect is not SE friendly and shouldn`t pass link juice. You can create proper 301 redirection using php header:

<?
Header( "HTTP/1.1 301 Moved Permanently" );
Header( "Location: http://www.new-url.com" );
?>