Multiple CGI parameters

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

We all know that to get some parameters from CGI, you do:

use CGI;
my $cgi = new CGI();
my $param1 = $cgi->param('param1');
my $param2 = $cgi->param('param2');
..
[download]

When I have a lot of parameters, copy-pasting the $cgi-param('..') over and over gets annoying quickly. Back before I put use strict; in my scripts (about three days ago), I would do the following to overcome this:

@params = ('param1', 'param2', ..);
for $param (@params) {
 $$param = $cgi->param($param);
}
[download]

However, now that I'm using strict, I can't do this anymore. I get an error that I can't declare a scalar dereference. I see that you can do things like:

my @names = $cgi->param;
[download]

$cgi->import_names('Q');
[download]

They just aren't as convenient as the other method. With the other method, I could get all the variables and then do things like

print "bla bla $param1 bla\n";
[download]

But now I would have to do something like

print "bla bla " . $Q::param1 . " bla\n";
[download]

I know I'm complaining about something that really doesn't matter too much. I'm just wondering what you monks do when you retrieve a large set of parameters. Although there are a plethora of other threads that deal with getting parameters with CGI.pm, I couldn't find any that answer this question. My apologies if such a thread already exists.

Thanks!

Comment on Multiple CGI parameters Select or Download Code

Replies are listed 'Best First'.
Re: Multiple CGI parameters by injunjoel (Priest) on Aug 15, 2008 at 18:57 UTC
Greetings, For some reason my first attempt at posting didn't work out No matter... I would suggest looking at the Vars() method/function in CGI, which will give you all your parameters in a nice neat hash. There is also example code to handle multi-valued parameters. -InjunJoel "I do not feel obliged to believe that the same God who endowed us with sense, reason and intellect has intended us to forego their use." -Galileo	[reply]
Re^2: Multiple CGI parameters by Joost (Canon) on Aug 15, 2008 at 19:48 UTC
Vars does have its problems (mainly, it concatenates duplicate variables, using the "\0" character) But in general, using a hash really is a lot more secure than trying to do what the OP wants. Especially considering that perl uses quite a lot of special variables that could be overwritten that way (and that's assuming the code itself uses lexicals exclusively, which it probably doesn't). "What should it profit a man, if he should win a flame war, yet lose his cool?"	[reply]
Re^3: Multiple CGI parameters by Cap'n Steve (Friar) on Aug 15, 2008 at 23:17 UTC
(mainly, it concatenates duplicate variables, using the "\0" character) I just ran into that issue and spent a few days trying to figure out what I thought was a UTF-8 encoding issue. So much fun.	[reply]
Re: Multiple CGI parameters by jhourcle (Prior) on Aug 15, 2008 at 16:09 UTC
The great thing about 'use strict' is that when you know that it's being a problem, you can turn it off: `for $param (@params) { no strict 'refs'; $$param = $cgi->param($param); }` [download] however, in your case, as everything's a scalar, I'd probably use the 'Vars' function to just dump it all to a hash: (or hashref, in this particular example) `use CGI ':cgi-lib'; $params = Vars;` [download] Update: chromatic is completely correct. You shouldn't turn off strict unless you're sure it's a good idea, as it can get you into trouble. If you're going to use the above trick, `@params` should come from a list that you define, and not from a call to `params()` or anything that might be tainted.	[reply] [d/l] [select]
Re^2: Multiple CGI parameters by chromatic (Archbishop) on Aug 15, 2008 at 17:04 UTC
Disabling strict in this way is a very bad idea. PHP used to do this, but after several years of PHP applications being broken into by malicious users automatically overwriting global variables by passing in carefully-crafted parameters, even PHP disabled this feature. You should not recommend that anyone do this.	[reply]
Re^2: Multiple CGI parameters by sstevens (Scribe) on Aug 15, 2008 at 16:25 UTC
`no strict 'refs';` [download] ~~Now that is cool! Thanks!~~ Update: Okay, okay, it isn't cool. I'm still just using the repetitive version.	[reply] [d/l]
Re^3: Multiple CGI parameters by FunkyMonk (Chancellor) on Aug 15, 2008 at 22:59 UTC
It's not cool. It's not big and it's not clever. You need to have a very good reason to turn off strict or warnings. This wasn't a good reason Unless I state otherwise, all my code runs with strict and warnings	[reply]
Re: Multiple CGI parameters by Lawliet (Curate) on Aug 15, 2008 at 15:43 UTC
I think I am misunderstanding the problem here. Why is `print "bla bla $params[0] bla\n";` not as convenient as `print "bla bla $param1 bla\n";` ? I'm so adjective, I verb nouns! chomp; # nom nom nom	[reply] [d/l] [select]
Re^2: Multiple CGI parameters by sstevens (Scribe) on Aug 15, 2008 at 16:07 UTC
You're right, it's just as convenient. The only problem is it would be hard to keep track of which parameters are where if accessed via `$params[0]`, `$params[1]`, etc. This is assuming that the parameters aren't actually `param1, param2, ..`, but something like `id, pw, ..`. If they were just `param1, param2, ..`, then that would work just fine!	[reply] [d/l] [select]
Re: Multiple CGI parameters by Anonymous Monk on Aug 15, 2008 at 14:45 UTC
use a hash	[reply]


We don't bite newbies here... much
	PerlMonks