PHP remove HTTP header

Something, I think Apache, adds these HTTP headers to all responses generated by PHP scripts:

Expires:   Thu, 19 Nov 1981 08:52:00 GMT
Cache-Control:  no-store, no-cache, must-revalidate, post-check=0, pre-check=0

This works ok for actual dynamic pages, but I have some page that, while generated by PHP, are mostly static, and I want the browser to cache them.

Is there a way in PHP to remove those headers from the response, and thus activate the browser’s default caching rules, or if not, is there any value I can set them to that’s equivalent with them being absent?

I would prefer not to set my own values, because I want the browser to use the same caching rules as for static resources that are served by Apache itself (without using mod_cache).

Answer

First I’d check if it really isn’t one of the php scripts that sets these headers.

register_shutdown_function('foo');
echo "test";

function foo() {
  flush();
  $c = "headers_list: n  " . join("n  ", headers_list());

  if ( function_exists('apache_response_headers') ) {
    $c .= "napache_response_headers:";
    foreach( apache_response_headers() as $k=>$v) {
      $c.= "n  $k=$v";
    }
  }
  $c .= "nn";
  echo '<pre>', $c, '</pre>';
}

Does this print something “usable” on your server?