Re: PHP 4.0 Bug #8017: PHP ignores "If-Modified-Since" headers

Hi Frank, > >Again, I still think PHP should automatically handle If-Modified-Since > >itself, by sending back a 304 response code and no content if the PHP script > >sends out a Modified header which is less than or equal to > >If-Modified-Since. As I've said, CGI scripts written in non-web languages > >such as Perl or sh do this automatically (i.e. with *no* special coding at > >all), so IMHO it only stands to reason that a high-level language like PHP > >should too. > > > > How can the PHP engine determine wheter or not the content of a script has changed ? By examining the Last-Modified header the script sends out. I'm not proposing that PHP "read the mind" of the script. Instead, very simply, if a Last-Modified header sent out by the script is less than or equal to If-Modified-Since, PHP should send out a 304 code and no body. This is in accordance with the HTTP spec. (See my response to Stanislav Malyshev's mail where I explain this in a bit more detail.) > The script can contain data from a database or any other source. This information can > only come from the script. The client sends a header with information on last modified > the php engine can only compare this to the file date of the script but that will not be > valid if the data in the database has changed. The PHP engine could compare the If-Modified-Since header against the Last-Modified header that the script sends out. In pseudo-code, it would work something like this: if (php script sent a Last-Modified header) { if (If-Modified-Since exists && Last-Modified > If-Modified-Since) { send out a 304 code; don't output any body; //...but let the script keep on executing return; } } Does that make sense? > I would say the same goes for shell scripts. How would the server or the script know about > changes in the conten if it was not checked by the script ? Neither PHP, the web server, nor the web browser should be concerned about changes in the content. All PHP should be doing is checking the Last-Modified date against the If-Modified-Since date to see if it should be sending out a body or not. Jordan Russell