Apache: The Definitive Guide, 3rd Edition

Data from a link

If your Apache Config file invokes CGI processing with the directive ScriptAlias, you can construct links in your HTML that have extra data passed with them as if they were directory names passed in the Environment variable PATH_INFO. For instance:

...
<A HREF="/cgi-bin/script2_html/whole_database">Click here to see whole database</A>
...

When the user clicks on this link she invokes script2_html and makes available to it the Environment variable PATH_INFO, containing the string /whole_database. We can test this in our Perl script with this:

if($ENV{'PATH_INFO'} eq '/whole_database')
{
#do something
}

Our script can then make a decision about what to do next on the basis of this information. The same mechanism is available with the HTML FORM ACTION attribute. We might set up a form in our HTML with the command:

<FORM METHOD='POST' ACTION="/cgi-bin/script2_html/receipts">

As previously, /receipts will turn up in PATH_INFO, and your script knows which form sent the data and can go to the appropriate subroutine to deal with it.

What happens inside Apache is that the URI — /cgi-bin/script2_html/receipts — is parsed from right to left, looking for a filename, which does not have to be a CGI script. The material to the right of the filename is passed in PATH_INFO.