http://qs321.pair.com?node_id=10955

mt2k has asked for the wisdom of the Perl Monks concerning the following question:

This is a pretty easy (for you) and dumb question, but...
How can I check the value of a checkbox after an html for is submitted.
Shouldn't I be able to go ($input contains my html form content:
if ($input{'checkbox1'} eq "on") {

I have even tried:
if ($input{'checkbox1'} ne "") {
Help me!!!

Thanx

Replies are listed 'Best First'.
Re: How to check value of checkbox on form submit?
by cei (Monk) on May 10, 2000 at 21:54 UTC
    All of this is assuming, of course, that you are passing a value to $input. You didn't really specify how you were parsing the form results. One way is the following: 
    #!/usr/bin/perl -w

use CGI;
use strict;
my $page = CGI::new();
my $input = $page->param('checkbox1');
if ($input eq 'on') {
    # do something
} else {
    # do something else
}
exit (0);

    [download]
    with the HTML set like the others have suggested, giving a value of "on" to the checkbox named "checkbox1".
[reply]
[d/l]
Re: How to check value of checkbox on form submit?
by comatose (Monk) on May 10, 2000 at 18:45 UTC

    Checkboxes don't have values unless you give them one. If they are checked, the name=value pair is sent. Otherwise, IIRC, nothing is sent. So in your HTML, you need:

    <input type="checkbox" name="blort" value="foo">

    [download]
    When you receive your form input, "blort" will equal "foo" if checked. If it isn't checked, "blort" will be undefined.

[reply]
[d/l]
      In other words, your form will work if your HTML is exactly like this:
      <input type="checkbox" name="checkbox1" value="on">

      [download]
      Then value=pair in this case would be checkbox1=on (if checked obviously). I disagree that if not checked your $input{'checkbox1'} would be undefined. That would vary depdending on the query string parsing method. It may be null, but not necessarily undef. This might be a source for errors down the road.
[reply]
[d/l]
        If the checkbox is not checked then it will not get posted to the query string. There will be no reference what-so-ever to the paramater (checkbox1 in this case). So the exists function mention below would probably be the easiest.

        Maybe this is just with my server (Apache), but I dont think so.
[reply]
        However, just setting a value of on in the html and then checking for that value in the script should always work. Whether undefined or null, it definately won't equal the string "on" so...
[reply]
Re: How to check value of checkbox on form submit?
by chromatic (Archbishop) on May 10, 2000 at 19:24 UTC
    How about: 
    if (defined ($cb_value = $input{checkbox1}) {
    # do something
} else {
    # do something less exciting
}

    [download]
    That will give you the value, if it's defined, or let you throw an error or rerequest the data, if necessary.
[reply]
[d/l]
Re: How to check value of checkbox on form submit?
by plaid (Chaplain) on May 10, 2000 at 20:30 UTC
    You might want to take a look at the exists function. It does exactly what you're looking for: tells you if a hash key exists, regardless of what its value is. 
    if(exists $input{'checkbox1'}) {

    [download]
    This will work regardless of what the value of the checkbox is, as the hash key 'checkbox1' will not exist unless the checkbox is checked.
[reply]
[d/l]

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