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Answer: How do I get data from a web form (the correct way)?

by andye (Curate)
on Dec 11, 2001 at 18:07 UTC ( #130927=categorized answer: print w/replies, xml ) Need Help??

Q&A > CGI programming > How do I get data from a web form (the correct way)? - Answer contributed by andye

Hi Monolith-0, you sound (understandably) frustrated. I'll try and clear things up a little.

First, you need to have the CGI.pm module installed. You almost certainly do already, as it comes as standard (I believe).

Second, you need to use it as part of your script. There are two ways of doing this, the object-oriented style, and the 'normal' style. I'll show you examples of both.

You need to make your HTML form. This is just a normal form, so I won't go into it - except to say that the action of the form should be the URL of your script.

Now, examples. The CGI.pm docs are here:
http://search.cpan.org/doc/LDS/CGI.pm-2.78/CGI.pm
Here are the examples at the top of that file, in 'normal' format:

use CGI qw/:standard/; print header, start_html('A Simple Example'), h1('A Simple Example'), start_form, "What's your name? ",textfield('name'),p, "What's the combination?", p, checkbox_group(-name=>'words', -values=>['eenie','meenie','minie','moe'], -defaults=>['eenie','minie']), p, "What's your favorite color? ", popup_menu(-name=>'color', -values=>['red','green','blue','chartreuse']),p, submit, end_form, hr; if (param()) { print "Your name is",em(param('name')),p, "The keywords are: ",em(join(", ",param('words'))),p, "Your favorite color is ",em(param('color')), hr; }
and OO format:
#!/usr/local/bin/perl -w use CGI; # load CGI routines $q = new CGI; # create new CGI object print $q->header, # create the HTTP header $q->start_html('hello world'), # start the HTML $q->h1('hello world'), # level 1 header $q->end_html; # end the HTML
I prefer the OO format, but you can use either. Note also that you don't have to use the output functions (e.g. $q->h1('hello world') in order to use the input functions (e.g.$q->param('foo'))

So, the most basic example of parsing form input would be:

my $query = new CGI; my $cheese = $query->param('cheese');
assuming that the HTML form has an input field called "cheese", e.g. <input type="text" name="cheese">

If you need to copy your parameters into a hash, then have a look at this part of the CGI.pm documentation:
http://search.cpan.org/doc/LDS/CGI.pm-2.78/CGI.pm#FETCHING_THE_PARAMETER_LIST_AS_A_HASH_.
NB: you need to pay special attention to what this says about 'multivalued CGI parameters', i.e. if there's more than one input tag in the form which has the same name, as in the case of checkboxes. Note also that if you're not using the OO style, then in order to use the  Vars() function, you need to use CGI ':cgi-lib'; (instead of the normal qw(:standard) ) at the start of your script.

Further answers can be found in the CGI.pm documentation and in O'Reilly's CGI Programming with Perl (Scott Guelich et al).

Hope that helps,
andy.

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