[PATCH] Allow unsetting headers previously set by header()

When a header has been set using header('Foo: bar') it can be replaced with other headers, but it cannot be removed. For instance, one could imagine that the auto_prepend_file calls header('Vary: Accept-Language') because most pages do language-negotiation. But if a single file generates, say, an image, it would improve caching if the Vary header was removed. Setting it to the empty string using header('Vary:') is not equivalent to unsetting the header. I suggest extending the behaviour of header() so that when the first argument does not contain a colon (and does not begin with "HTTP/"), e.g. header('Vary'), it unsets the header with the specified name. AFAICT this change is backwards compatible. According to the HTTP spec, RFC 2616, section 4.2, header lines must include a colon, so calling e.g. header('Vary') does currently not generate a valid header: http://www.w3.org/Protocols/rfc2616/rfc2616-sec4.html#sec4.2 The attached patch contains an implementation for the cgi and apache2handler SAPIs. AFAICT these SAPIs don't need to be changed: cli, embed, isapi, milter, pi3web, thttpd, tux, webjames. These SAPIs need additional patching: apache, apache_hooks, apache2filter, continuity/capi, caudium, nsapi, phttpd, roxen I don't have an easy way to test these SAPIs, so any help with adding support for them is appreciated. AFAICT some of these don't have full header() support (in particular for the second $replace parameter), so it may not be a big issue if they aren't patched right away. For some reason I couldn't build apache2filter on my machine. The atteched phpt file is intended to be put in ext/standard/tests/general_functions. What do you think of the general idea of being able to unset headers? And what do you think of my patch? This is my first patch for PHP. I am not a strong C programmer. Christian