NAME
    Apache::SSI - Implement Server Side Includes in Perl

SYNOPSIS
    In httpd.conf:

        <Files *.phtml>  # or whatever
        SetHandler perl-script
        PerlHandler Apache::SSI
        </Files>

    You may wish to subclass Apache::SSI for your own extensions. If so,
    compile mod_perl with PERL_METHOD_HANDLERS=1 (so you can use object-
    oriented inheritance), and create a module like this:

        package MySSI;
        use Apache::SSI ();
        @ISA = qw(Apache::SSI);

        #embedded syntax:
        #<!--#something param=value -->
        sub ssi_something {
           my($self, $attr) = @_;
           my $cmd = $attr->{param};
           ...
           return $a_string;   
        }
     
     Then in httpd.conf:
     
        <Files *.phtml>
         SetHandler perl-script
         PerlHandler MySSI
        </Files>

DESCRIPTION
    Apache::SSI implements the functionality of mod_include for handling
    server-parsed html documents. It runs under Apache's mod_perl.

    In my mind, there are two main reasons you might want to use this
    module: you can sub-class it to implement your own custom SSI
    directives, and/or you can parse the output of other mod_perl handlers,
    or send the SSI output through another handler (use Apache::Filter to do
    this).

    Each SSI directive is handled by an Apache::SSI method with the prefix
    "ssi_". For example, <!--#printenv--> is handled by the ssi_printenv
    method. attribute=value pairs inside the SSI tags are parsed and passed
    to the method in a hash reference.

    'Echo' directives are handled by the ssi_echo method, which delegates
    lookup to methods with the prefix "echo_". For instance, <!--#echo
    var=DOCUMENT_NAME--> is handled by the echo_DOCUMENT_NAME method.

    You can customize behavior by inheriting from Apache::SSI and overriding
    'ssi_*' and 'echo_*' methods, or writing new ones.

  SSI Directives

    This module supports the same directives as mod_include. At least,
    that's the goal. =) For methods listed below but not documented, please
    see mod_include's online documentation at http://www.apache.org/ .

    * config
    * echo
    * exec
    * fsize
    * flastmod
    * include
    * printenv
    * set
    * perl
        There are two ways to call a Perl function, and two ways to supply
        it with arguments. The function can be specified either as an
        anonymous subroutine reference, or as the name of a function defined
        elsewhere:

         <!--#perl sub="sub { localtime() }"-->
         <!--#perl sub="time::now"-->

        If the 'sub' argument matches the regular expression
        /^\s*sub[^\w:]/, it is assumed to be a subroutine reference.
        Otherwise it's assumed to be the name of a function. In the latter
        case, the string "main::" will be prepended to the function name if
        the name doesn't contain "::" (this forces the function to be in the
        main package, or a package you specify). Note that it's a pretty bad
        idea to put your code in the main package, so I only halfheartedly
        endorse this feature.

        In general, it will be slower to use anonymous subroutines, because
        each one has to be eval()'ed and there is no caching. For best
        results, pre-load any code you need in the parent process, then call
        it by name.

        If you're calling a subroutine like "&Package::SubPack::handler",
        you can omit the "handler" portion, making your directive like this:

         <!--#perl sub="Package::Subpack"-->

        If you want to supply a list of arguments to the function, you use
        either the "arg" or the "args" parameter:

         <!--#perl sub="sub {$_[0] * 7}" arg=7-->
         <!--#perl sub=holy::matrimony arg=Hi arg=Lois-->
         <!--#perl sub=holy::matrimony args=Hi,Lois-->

        The "args" parameter will simply split on commas, meaning that
        currently there's no way to embed a comma in arguments passed via
        the "args" parameter. Use the "arg" parameter for this.

        If you give a key-value pair and the key is not 'sub', 'arg',
        'args', or 'pass_request' (see below), then your routine will be
        passed both the key and the value. This lets you pass a hash of key-
        value pairs to your function:

         <!--#perl sub=holy::matrimony groom=Hi bride=Lois-->
         Will call &holy::matrimony('groom', 'Hi', 'bride', 'Lois');

        As of version 1.95, we pass the current Apache request object ($r)
        as the first argument to the function. To turn off this behavior,
        give the key-value pair 'pass_request=no', or put 'PerlSetVar
        SSIPerlPass_Request no' in your server's config file.

        See `http://perl.apache.org/src/mod_perl.html' for more information
        on Perl SSI calls.

    * if
    * elif
    * else
    * endif
        These four directives can be used just like in `mod_include', with
        one important difference: the boolean expression is evaluated using
        Perl's eval(). This means you use `==' or `eq' instead of `=' to
        test equality. It also means you can use pre-loaded Perl subroutines
        in the conditions:

         <!--#if expr="&Movies::is_by_Coen_Brothers($MOVIE)"-->
          This movie is by the Coen Brothers.
         <!--#else-->
          This movie is not by the Coen Brothers.
         <!--#endif-->

        It can't handle very sophistocated Perl though, because it manually
        looks for variables (of the form $var or ${var}, just like
        `mod_include'), and will get tripped up on expressions like $object-
        >method or $hash{'key'}. I'll welcome any suggestions for how to
        allow arbitrary Perl expressions while still filling in Apache
        variables.

CHAINING HANDLERS
    There are two fairly simple ways for this module to exist in a stacked
    handler chain. The first uses `Apache::Filter', and your httpd.conf
    would look something like this:

     PerlModule Apache::Filter
     PerlModule Apache::SSI
     PerlModule My::BeforeSSI
     PerlModule My::AfterSSI
     <Files ~ "\.ssi$">
      SetHandler perl-script
      PerlSetVar Filter On
      PerlHandler My::BeforeSSI Apache::SSI My::AfterSSI
     </Files>

    The `"PerlSetVar Filter On"' directive tells the three stacked handlers
    that they should use their filtering mode. It's mandatory.

    The second uses `Apache::OutputChain', and your httpd.conf would look
    something like this:

     PerlModule Apache::OutputChain
     PerlModule Apache::SSIChain
     PerlModule My::BeforeSSI
     PerlModule My::AfterSSI
     <Files ~ "\.ssi$">
      SetHandler perl-script
      PerlHandler Apache::OutputChain My::AfterSSI Apache::SSIChain My::BeforeSSI
     </Files>

    Note that the order of handlers is reversed in the two different
    methods. One reason I wrote `Apache::Filter' is to get the order to be
    more intuitive. Another reason is that `Apache::SSI' itself can be used
    in a handler stack using `Apache::Filter', whereas it needs to be
    wrapped in `Apache::SSIChain' to be used with `Apache::OutputChain'.

    Please see the documentation for `Apache::OutputChain' and
    `Apache::Filter' for more specific information. And look at the note in
    CAVEATS too.

CAVEATS
    * When chaining handlers via Apache::Filter, if you use <!--#include
    ...--> or <!--#exec cgi=...-->, then Apache::SSI must be the last filter
    in the chain. This is because Apache::SSI uses $r->lookup_uri(...)->run
    to include the files, and this sends the output through C's stdout
    rather than Perl's STDOUT. Thus Apache::Filter can't catch it and filter
    it.

    If Apache::SSI is the last filter in the chain, or if you stick to
    simpler SSI directives like <!--#fsize-->, <!--#flastmod-->, etc. you'll
    be fine.

    * Currently, the way <!--#echo var=whatever--> looks for variables is to
    first try $r->subprocess_env, then try %ENV, then the five extra
    environment variables mod_include supplies. Is this the correct order?

TO DO
    Revisit http://www.apache.org/docs/mod/mod_include.html and see what
    else there I can implement.

    It would be nice to have a "PerlSetVar ASSI_Subrequests 0|1" option that
    would let you choose between executing a full-blown subrequest when
    including a file, or just opening it and printing it.

    I'd like to know how to use Apache::test for the real.t test.

SEE ALSO
    mod_include, mod_perl(3), Apache(3), HTML::Embperl(3), Apache::ePerl(3),
    Apache::OutputChain(3)

AUTHOR
    Ken Williams ken@forum.swarthmore.edu

    Concept based on original version by Doug MacEachern dougm@osf.org .
    Implementation different.

COPYRIGHT
    Copyright 1998 Swarthmore College. All rights reserved.

    This library is free software; you can redistribute it and/or modify it
    under the same terms as Perl itself.