Perl - CGI.pm module: Object Oriented CGI package

This is an overview of the Perl CGI.pm package and its use in CGI programming. You should have read before my Perl - Object-Oriented Programming Concepts tutorial. CGI.pm is a more powerful library but it requires Perl 5 and is part of the object-oriented Perl libraries. Example 17 shows the form-decode script we seen previously using CGI.pm. You can also see it working here. For a comparison of cgi-lib.pl and CGI.pm see this page.

Basics

• Invoking and instantiating. CGI.pm is an object-oriented module, therefore in order to use it you need to create an instance of the CGI object using its constructor method. You can see below how to invoke CGI.pm and create the instance:
  use CGI;
  
  $request = CGI::new();        # creating the instance

  You can also invoke CGI.pm specifying that you want to import its methods:

  use CGI qw(:standard);

  The advantage of doing so is that you no longer need to instantiate the CGI object, CGI.pm will do it for you. You also no longer need to use the CGI module reference. In this example you see how this simplifies the coding:

  use CGI qw(:standard);
  
  print header;
  
  print start_html('Example 1');

  Applying methods. Use the -> notation to apply methods to the CGI object instance. Here is an example of a very simple script using CGI.pm:

  #!/usr/bin/perl -w
  

  #cgi script with CGI.pm

  use CGI;
  

  $request = CGI::new();
  

  print $request->header();
  

  print $request->h1("Hello World!");

  You can compare with doing without a CGI library, and using cgi-lib.pl. If you import the CGI.pm methods and do not use the -> notation you could write the script as:

  use CGI qw(:standard);
  

  print header;
  

  print h1("Hello World!");

Basic Methods

cgi-lib.pl	description	CGI.pm	syntax	example ($q is instance)
PrintHeader	generates the required header for a server reply	header ( )	header(content type,status,headers)	print $q->header; or print header;
ReadParse	decode form information and place results in %in and @in	ReadParse( )	ReadParse (only %in)	ReadParse;
		param ( )	@name= param or param("key1","key2", ...);	$meal = $q->param('order'); or $meal = param('order');
MethGet	returns true if method is GET, false if POST	request_method ( )	request_method	if (request_method) { .........}
HtmlTop	initial HTML tags of a page. You can specify the TITLE: &HtmlTop(This)	start_html ( )	start_html (-title =>"value",-atribute=> "value", ...	print start_html (-title=>"Example of CGI.pm",-BGCOLOR=>"white");
HtmlBot	returns the closing HTML tags of a page.	end_html ( )	end_html	print end_html;
MyFullUrl	returns the full URL of the script	self_url	self_url	print self_url;

Other Methods

This page is maintained by Al Bento who can be reached at abento@ubmail.ubalt.edu. This page was last updated on October 7, 2002. Although we will attempt to keep this information accurate, we can not guarantee the accuracy of the information provided.