What is the purpose of the P3P HTTP Header in PHP and how does it affect cross-site cookies?

The purpose of the P3P HTTP Header in PHP is to address cross-site cookie issues by specifying a compact privacy policy that browsers can use to determine whether they should accept cookies from a third-party domain. This header helps prevent cookie blocking and allows for proper cookie handling across different domains.

header('P3P: CP="NOI ADM DEV PSAi COM NAV OUR OTRo STP IND DEM"');