PHP remove HTTP header

Question

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 1

For those particular files you could add header() calls that set those headers differently. ie. header("Expires: " . $currentDatePlus10);

header("Cache-Control: max-age=3600, must-revalidate")

Answer 2

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 .= "\n\n";
  echo '<pre>', $c, '</pre>';
}

Does this print something "usable" on your server?

Answer 3

You can manually provide HTTP headers from PHP via the header() function.

I'd imagine that doing so ought to disable the web server's default header values.

Answer 4

These cache headers are sent when you start using sessions and set to "nocache" by default; this makes sure each request gives consistent results.

For instance, if you have a cart system and your browser caches /add?product=xyz, it may not add the product again; this is probably not what you want.

Having said that, the default setting can be changed by either using session_cache_limiter() before session_start() or setting the corresponding session.cache_limiter configuration setting.

Answer 5

header("Expires: Fri, 1 Jan 2038 05:00:00 GMT");

or some equally absurd time in the distant future. Remember to set your header values before any output has been sent, unless you're doing output buffering for your entire page.

http://php.net/manual/en/function.header.php

Answer 6

If your pages are changing not to often you should consider using Etag headers, like this:

https://gist.github.com/oliworx/4951478

This is useful especially on slow connections (like mobile phones).

Hint: You should always check, what the browser is really loading, with the firefox addon "Live HTTP headers": https://addons.mozilla.org/de/firefox/addon/live-http-headers/

Answer 7

suppress that of the cache can be made as follows: PHP Code:

header ( "Cache-Control: no-cache, must-revalidate"); / / HTTP/1.1
header ( "Expires: Mon, 1 Jul 1990 05:00:00 GMT"); / / Date in the past

if you want to automatically generate it, then you this here: PHP: session_cache_limiter() - Manual they

Answer 8

There is likely somewhere in your code that has set these variables, as I can't find where they are inserted automatically by PHP anywhere, nor are they in any of my LAMP installations.

The only automatically generated header for my installs is X-Powered-By with the PHP version.

As you've said, from the docs they recommend saying header("Expires:"); to replace the old header, but header("Cache-control:"); just became Cache-Control: max-age=0 in my browser (so this is not what you're trying to do).

I'd recommend checking if these values come from a framework or setting you've changed, but it may be different across different versions of PHP / platforms you'd be running PHP on.

I'd check for ExpiresByType or ExpiresDefault directives in global configs, vhosts, pr .htaccess files or any blocks encapsulated in <IfModule mod_expires> or <IfModule mod_expires.c>

"I want the browser to use the same caching rules as for static resources that are served by Apache itself (without using mod_cache)."

Try looking at a static resource and then matching the rules then. You can calculate the Expires offest with this -> http://www.php.net/manual/en/function.header.php#93377

Answer 9

I have not tried this but you could probably save such pages as .html files with your custom headers or lack of their-of and the script could run inside the