Is $formdata present?

ecuguru has asked for the wisdom of the Perl Monks concerning the following question:

Hi
I've got code below (copy/pasted) that works for grabbing data from a post/get request.
Can someone tell me what function I can use to check to see if a value was submitted or not? I have played with exists and defined, but couldn't get either to work right.
A user can post and id and another number. If the number isn't provided, I have a default number that I replace it with later. But I can't figure out how to tell perl that if the value isn't submitted, tell me.

Any ideas? And Thanks in advance!

if ($ENV{'REQUEST_METHOD'} eq 'GET') {
        @pairs = split(/&/, $ENV{'QUERY_STRING'});
} elsif ($ENV{'REQUEST_METHOD'} eq 'POST') {
        read (STDIN, $buffer, $ENV{'CONTENT_LENGTH'});
        @pairs = split(/&/, $buffer);
} else {
        print "Content-type: text/html\n\n";
        print "<P>Use Post or Get";
}

foreach $pair (@pairs) {
        ($key, $value) = split (/=/, $pair);
        $key =~ tr/+/ /;
        $key =~ s/%([a-fA-F0-9] [a-fA-F0-9])/pack("C", hex($1))/eg;
        $value =~ tr/+/ /;
        $value =~ s/%([a-fA-F0-9] [a-fA-F0-9])/pack("C", hex($1))/eg;
        
        $value =~s/<!--(.|\n)*-->//g;
        
        if ($formdata{$key}) {
                $formdata{$key} .= ", $value";
        } else {
                $formdata{$key} = $value;
        }
}

$id = $formdata{'id'};
$num = $formdata{'num'};      #If there great, if not how do i know?
$num = sprintf("%3.3f",$num);  #if num is not present, this makes num 
+0.
[download]

Comment on Is $formdata present? Download Code

Replies are listed 'Best First'.
Re: Is $formdata present? by blazar (Canon) on Jun 07, 2005 at 08:46 UTC
Possibly OT wrt your actual question - I must admit I didn't even read it carefully. I have only extremely limited experience myself. But they all recommend to avoid reinventing the wheel with the risk of doing it wrong and `use CGI;` [download] instead. And I mean experienced hackers that could well reinvent the wheel...	[reply] [d/l]
Re: Is $formdata present? by stonecolddevin (Parson) on Jun 07, 2005 at 09:59 UTC
Ewwwwwiiie! use CGI, and read Ovid's CGI course on how to use it and why. You'll come to find that manually trying to parse form data gets tiresome and leads to broken code 9/10 times¹. ¹ Statistics not validated by the FDA or any other official affiliation. meh.	[reply]
Re: Is $formdata present? by tchatzi (Acolyte) on Jun 07, 2005 at 08:49 UTC
I think you should consider reading the documentation of CGI. You can find it here CGI . It will be easier for you, if you use CGI to work with forms. ``The wise man doesn't give the right answers, he poses the right questions.'' TIMTOWTDI	[reply]
Re^2: Is $formdata present? by Anonymous Monk on Jun 07, 2005 at 09:03 UTC
Correct. CGi.pm will work for both POST and GET. For existence u couldd use something like.. `use CGI qw(:standard); my %formdata = (); map { $formdata{$_} = param($_); } param; if(exists $formdata{'parametername'}) {do something;}` [download] 20050606 Janitored by Corion: Added formatting, put code in between <code>...</code> tags	[reply] [d/l]
Re^3: Is $formdata present? by techcode (Hermit) on Jun 07, 2005 at 22:05 UTC
While using CGI.pm is a good thing, you still made it more complicated than it should be, at least if you ask me ... `use strict; use CGI; my $q = new CGI; my $form = $q->Vars(); if(exists $form->{parameter_name}){ #do whatever }` [download] Of course, you can also use Data::FormValidator. It's suggested if you need more complicated form validation.	[reply] [d/l]
Re^3: Is $formdata present? by ruoso (Curate) on Jun 07, 2005 at 18:33 UTC
And multipart-formdata encoding also, which you simply ignored.	[reply]
Re^3: Is $formdata present? by ecuguru (Monk) on Jun 07, 2005 at 17:45 UTC
So what's the difference functionally between Defined and Exists? I thought Exists was used for subroutines and hashes? (clearly wrong)..	[reply]
Re^3: Is $formdata present? by Anonymous Monk on Jun 07, 2005 at 09:08 UTC
Sorry.. I'm new. Will soon register myself and format my code. But my answer should work for you. Happy Coding	[reply]
Re: Is $formdata present? by jpeg (Chaplain) on Jun 07, 2005 at 09:11 UTC
would either of these work? if (length($formdata{'num'}) == 0) { #... } if ($formdata{'num'} eq '' ) { #... } obligatory 'use CGI' suggestion goes here -- jpg	[reply]
Re^2: Is $formdata present? by ecuguru (Monk) on Jun 07, 2005 at 17:40 UTC
Yes and no.. Yes it works and it will execute correctly. No because you get runtime warnings about trying to do operations with a nonexistant variable If you have your code online and hit enough times, it just jams up the error log something fierce.	[reply]