NAME
PLP - Perl in HTML pages
MODULE INSTALLATION
perl Makefile.PL
make
make test
make install
SYNOPSIS
mod_perl installation
* httpd.conf (for mod_perl setup)
<Files *.plp>
SetHandler perl-script
PerlHandler PLP
PerlSendHeader On
PerlSetVar PLPcache On
</Files>
# Who said CGI was easier to set up? :)
CGI installation
* /foo/bar/plp.cgi (local filesystem address)
#!/usr/bin/perl
use PLP;
PLP::everything();
* httpd.conf (for CGI setup)
ScriptAlias /foo/bar/ /PLP_COMMON/
<Directory /foo/bar/>
AllowOverride None
Options +ExecCGI
Order allow,deny
Allow from all
</Directory>
AddHandler plp-document plp
Action plp-document /PLP_COMMON/plp.cgi
Test script (test.plp)
<html><body>
<:
print "Hurrah, it works!<br>" for 1..10;
:>
</body></html>
DESCRIPTION
PLP is yet another Perl embedder, primarily for HTML documents. Unlike
with other Perl embedders, there is no need to learn a meta-syntax or
object model: one can just use the normal Perl constructs. PLP runs
under mod_perl for speeds comparable to those of PHP, but can also be
run as a CGI script.
PLP Syntax
"<: perl_code(); :>" With "<:" and ":>", you can add Perl code to your
document. This is what PLP is all about. All code
outside of these tags is printed. It is possible
to mix perl language constructs with normal HTML
parts of the document:
<: unless ($ENV{REMOTE_USER}) { :>
You are not logged in.
<: } :>
":>" always stops a code block, even when it is
found in a string literal.
"<:= $expression :>" Includes a dynamic expression in your document.
The expression is evaluated in list context.
Please note that the expression should not end a
statement: avoid semi-colons. No whitespace may be
between "<:" and the equal sign.
"foo <:= $bar :> $baz" is like "<: print 'foo ',
$bar, ' baz'; :>".
"<(filename)>" Includes another file before the PLP code is
executed. The file is included literally, so it
shares lexical variables. Because this is a
compile-time tag, it's fast, but you can't use a
variable as the filename. You can create recursive
includes, so beware! (PLP will catch simple
recursion: the maximum depth is 128.) Whitespace
in the filename is not ignored so "<( foo.txt)>"
includes the file named " foo.txt", including the
space in its name. A compile-time alternative is
include(), which is described in PLP::Functions.
PLP Functions
These are described in PLP::Functions.
PLP Variables
$ENV{PLP_NAME} The URI of the PLP document, without the query
string. (Example: "/foo.plp")
$ENV{PLP_FILENAME} The filename of the PLP document. (Example:
"/var/www/index.plp")
$PLP::VERSION The version of PLP.
$PLP::DEBUG Controls debugging output, and should be treated
as a bitmask. The least significant bit (1)
controls if run-time error messages are reported
to the browser, the second bit (2) controls if
headers are sent twice, so they get displayed in
the browser. A value of 3 means both features are
enabled. The default value is 1.
$PLP::ERROR Contains a reference to the code that is used to
report run-time errors. You can override this to
have it in your own design, and you could even
make it report errors by e-mail. The sub reference
gets two arguments: the error message as plain
text and the error message with special characters
encoded with HTML entities.
%header, %cookie, %get, %post, %fields
These are described in PLP::Fields.
(mod_perl only) PerlSetVar configuration directives
PLPcache Sets caching On/Off. When caching, PLP saves your
script in memory and doesn't re-read and re-parse
it if it hasn't changed. PLP will use more memory,
but will also run 50% faster.
On is default, anything that isn't =~ /^off$/i is
considered On.
Things that you should know about
Not only syntax is important, you should also be aware of some other
important features. Your script runs inside the package "PLP::Script"
and shouldn't leave it. This is because when your script ends, all
global variables in the "PLP::Script" package are destroyed, which is
very important if you run under mod_perl (they would retain their values
if they weren't explicitly destroyed).
Until your first output, you are printing to a tied filehandle "PLPOUT".
On first output, headers are sent to the browser and "STDOUT" is
selected for efficiency. To set headers, you must assign to $header{
$header_name} before any output. This means the opening "<:" have to be
the first characters in your document, without any whitespace in front
of them. If you start output and try to set headers later, an error
message will appear telling you on which line your output started. An
alternative way of setting headers is using Perl's BEGIN blocks. BEGIN
blocks are executed as soon as possible, before anything else.
Because the interpreter that mod_perl uses never ends, "END { }" blocks
won't work properly. You should use "PLP_END { };" instead. Note that
this is a not a built-in construct, so it needs proper termination with
a semi-colon (as do <eval> and <do>).
Under mod_perl, modules are loaded only once. A good modular design can
improve performance because of this, but you will have to reload the
modules yourself when there are newer versions.
The special hashes are tied hashes and do not always behave the way you
expect, especially when mixed with modules that expect normal CGI
environments, like CGI.pm. Read PLP::Fields for information more about
this.
FAQ and HowTo
A lot of questions are asked often, so before asking yours, please read
the FAQ at PLP::FAQ. Some examples can be found at PLP::HowTo.
NO WARRANTY
No warranty, no guarantees. Use PLP at your own risk, as I disclaim all
responsibility.
AUTHORS
Currently maintained by Mischa POSLAWSKY <perl@shiar.org>
Originally by Juerd Waalboer <juerd@cpan.org>
SEE ALSO
PLP::Functions, PLP::Fields, PLP::FAQ, PLP::HowTo