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Table of Contents
Open Source Web Development with LAMP: Using Linux, Apache, MySQL, Perl, and PHP
By
James Lee, Brent Ware
Topics covered include:
A comprehensive survey of Open Source technologiesStatic and dynamic data and embedded HTML on the WebLinux and Unix distributions, installations, and commandsApache Web Server, Perl, and MySQLWeb site META language (WML)Common gateway interface (CGI) and mod_perlServer Side Includes (SSI), Embperl, and MasonPHP syntax and functionsIn addition to the discussions in the book, a companion Web site-www.opensourcewebbook.com-contains supplemental information, including tools, source code, helpful links to additional resources, and errata as needed.Complete in coverage and practical in presentation, Open Source Web Development with LAMP spotlights the tools and technologies today''''s developers need to create workable, dynamic, and secure Web sites using Open Source technologies.
7.5 CGI.pm Introduced
So far, this has been pretty thin gruel. To do more complicated things in an easier fashion, we introduce the Perl/CGI programmer's friend: CGI.pm.CGI.pm is a Perl module written by Lincoln Stein. Our discussion of CGI.pm is just an introduction. Much more documentation is available. We recommend that you check out Lincoln Stein's Official Guide to Programming with CGI.pm [Stein 98]. You can also check out the CGI.pm documentation with perldoc CGI.To use CGI.pm, tell Perl that you want to use it with the use pragma:
use CGI;
After Perl executes this statement, your program has access to all the methods that CGI.pm provides. The module can be further refined by specifying a more convenient programming style, called the standard style:
use CGI ´:standard´;
Here's an example of some simple HTML that creates Figure 7.7:
Figure 7.7. A simple page with CGI.pm
#!/usr/bin/perl
# simple.cgi
use CGI ´:standard´;
header(),
start_html(-title => ´A Simple Page´,
-bgcolor => ´#ffffff´,
-text => ´#520063´),
h1(´Hello, world! again´),
hr(),
´Time to go now...´,
end_html();
The fourth line indicates that we want to use the CGI.pm module, passing the string ´:standard´ into the use pragma. This ensures that we will use only functions that are appropriate for the widest range of browsers, up to HTML version 3. To use all the HTML there is, we could use CGI ´:all´;. These are the two most widely used options.The use of ´:standard´ also enables us to call CGI.pm methods such as hr() directly without an object. If we did not use ´:standard´ mode, we would have to create a CGI object and execute the methods with it, as in this code:
$q = new CGI;
$q->header(),
.
.
$q->hr(),
.
.
As you can see, using ´:standard´ mode is much nicerit looks cleaner and we avoid the difficult-to-type $q->. Also, using ´:standard´ ensures you of the widest possible audience because the HTML generated will support most major browsers.The rest of the program is all part of the same print() function call. We could have printed each piece separately, but the convention is to combine the multiple prints into a single print() function.These are the other methods used in this program.
header() generates the header "Content-type: text/html\n\n"; CGI.pm adds the extra newline automatically.
start_html()] generates the HTML for the start of the web page: <HTML><HEAD>...; within this, note the use of the following:
h1() generates an <H1> tag, and the argument is placed within the tags; in this example, the HTML produced is <H1>Hello, world! again</H1>.
hr() generates <HR>.
end_html() generates </BODY></HTML>.
This program can be run from the command line to see the output (enter ctrl-D after the offline mode prompt):
$ ./simple.cgi
(offline mode: enter name=value pairs on standard input)
^D
Content-Type: text/html
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">
<HTML><HEAD><TITLE>A Simple Page</TITLE>
</HEAD><BODY TEXT="#520063" BGCOLOR="#ffffff"><H1>Hello, world!
again</H1>
<HR>Time to go now...</BODY></HTML>
