apply_filters( ‘wp_headers’, string[] $headers, WP $wp )

User Contributed Notes

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   Nick C 11 years ago

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   This filter won’t allow you to modify headers if your site serves cached pages via a plugin or third-party caching system. The cached page will be served before your wp_headers are filtered.

   You may be able to add an HTML meta tag with the http-equiv attribute using wp_head() to work around this for certain headers: https://reference.sitepoint.com/html/meta/http-equiv

   function gnu_terry_pratchett_meta() {
       if ( WP_CACHE ) {
           echo '<meta http-equiv="X-Clacks-Overhead" content="GNU Terry Pratchett" />';
       }
   }
   add_action( 'wp_head', 'gnu_terry_pratchett_meta' );

   Alternatively, explore setting headers at the server level with .htaccess or similar if you can.

   header set X-Clacks-Overhead "GNU Terry Pratchett"