Bug #8017 Updated: PHP ignores "If-Modified-Since" headers

ID: 8017 Updated by: markonen@php.net Reported By: jr-php@quo.to -Status: Open +Status: Closed Bug Type: Feature/Change Request Operating System: Linux PHP Version: 4.2.1 New Comment: What kind of logic do you suggest PHP should use to determine whether the output of your script has indeed been modified since the IMS date sent by the user agent? Hint: we don't cache script output internally, so there is NO WAY for us to do that. As for www.php.net not returning 304 for you -- tough. It works for us. Some Internet Explorer versions have the unfortunate tendency of mangling the IMS date (ie. the IMS date is not the same as the Last-Modified date the UA received). Because we follow the RFC 2616 recommendation of checking for an exact match between the IMS date and our internal Last-Modified date, the IMS negotiation mechanism we have in place for www.php.net doesn't work on such user agents. Please check your user agent behaviour before concluding that this is a bug in PHP. Previous Comments: ------------------------------------------------------------------------ [2002-06-17 14:00:12] jr-php@quo.to (Changing back to 'Open' since you clearly misunderstood the request.) > as PHP itself can't know what the data you are > going to produce looks like or whether it has > changed since the last request in advance > without executing your code This is not about suppressing the execution of code. It's about PHP (mod_php) handling If-Modified-Since automatically in the same manner as CGI on Apache. This is possible, too, because I posted a proof-of-concept patch to the list. > PS: whatever the CGI script you are refering to > does, i'm rather sure that it deals with that > itself, too You're saying my 5 line /bin/sh CGI script somehow "deals" with If-Modified-Since headers? I think not... ------------------------------------------------------------------------ [2002-06-17 13:20:48] hholzgra@php.net it is in the responsibility of the application code to check for If-Modified-Since conditions and to send 304 Status codes, as PHP itself can't know what the data you are going to produce looks like or whether it has changed since the last request in advance without executing your code PS: whatever the CGI script you are refering to does, i'm rather sure that it deals with that itself, too ------------------------------------------------------------------------ [2000-11-29 11:57:24] stas@php.net moved to feature request ------------------------------------------------------------------------ [2000-11-29 11:52:34] jr-php@quo.to Closed since it doesn't appear to be a bug, but rather missing functionality in PHP. ------------------------------------------------------------------------ [2000-11-28 16:58:56] jr-php@quo.to PHP: 4.0.3p1 Apache: 1.3.14 Browser: IE 5.5 SP1 Because I want my PHP pages to be cached, my PHP script sends out a Last-Modified header (entire code follows): <?php Header ("Last-Modified: Mon, 27 Nov 2000 00:00:00 GMT"); ?> Test... One would think that this would be enough to get a web browser to cache the page, but evidently it is not. Examining my web server's access log shows that each time the page is subsequently requested (e.g. by pressing Refresh), it sends back a "200 OK" response code instead of a "304 Not Modified" as it should. In other words, the server is sending back a fresh copy of the page every time. However, if I do a similar thing using a CGI script, the server *does* send back "304" codes as it should (entire code follows): #!/bin/sh echo "Last-Modified: Mon, 27 Nov 2000 00:00:00 GMT" echo "Content-Type: text/html" echo "" echo "Test..." In both cases, an "If-Modified-Since" header is being sent to the server. Yet the PHP script appears to ignore it completely and send a fresh page, while the very simple CGI shell script doesn't. P.S. At the bottom of this are transcripts of the HTTP requests for the PHP & CGI scripts. Notice how PHP sends back a fresh page even though the If-Modified-Since date is the same as the Last-Modified date. P.P.S. I just noticed that this problem affects PHP's own web site too! The page http://www.php.net/ returns a Last-Modified header, but browsers receive a fresh copy of the page every time since If-Modified-Since is ignored. --- PHP script --- GET /test.php HTTP/1.0 If-Modified-Since: Mon, 27 Nov 2000 00:00:00 GMT HTTP/1.1 200 OK Date: Mon, 27 Nov 2000 20:41:29 GMT Server: Apache/1.3.14 (Unix) PHP/4.0.3pl1 X-Powered-By: PHP/4.0.3pl1 Last-Modified: Mon, 27 Nov 2000 00:00:00 GMT Connection: close Content-Type: text/html Test... --- CGI shell script --- GET /cgi-bin/test.cgi HTTP/1.0 If-Modified-Since: Mon, 27 Nov 2000 00:00:00 GMT HTTP/1.1 304 Not Modified Date: Mon, 27 Nov 2000 20:41:46 GMT Server: Apache/1.3.14 (Unix) PHP/4.0.3pl1 Connection: close ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=8017&edit=1