I’ve run into what appears to be a variable scope issue I haven’t encountered before. I’m using Perl’s CGI module and a call to DBI’s do() method. Here’s the code structure, simplified a bit:
use DBI; use CGI qw(:cgi-lib); &ReadParse; my $dbh = DBI->connect(...............); my $test = $in{test}; $dbh->do(qq{INSERT INTO events VALUES (?,?,?)},undef,$in{test},'$in{test}',$test); The #1 placeholder variable evaluates as if it is uninitialized. The other two placeholder variables work.
The question: Why is the %in hash not available within the context of do(), unless I wrap it in double quotes (#2 placeholder) or reassign the value to a new variable (#3 placeholder)?
I think it’s something to do with how the CGI module’s ReadParse() function assigns scope to the %in hash, but I don’t know Perl scoping well enough to understand why %in is available at the top level but not from within my do() statement.
If someone does understand the scoping issue, is there a better way to handle it? Wrapping all the %in references in double quotes seems a little messy. Creating new variables for each query parameter isn’t realistic.
Just to be clear, my question is about the variable scoping issue. I realize that ReadParse() isn’t the recommended method to grab query params with CGI.
I’m using Perl 5.8.8, CGI 3.20, and DBI 1.52. Thank you in advance to anyone reading this.
@Pi & @Bob, thanks for the suggestions. Pre-declaring the scope for %in has no effect (and I always use strict). The result is the same as before: in the db, col1 is null while cols 2 & 3 are set to the expected value.
For reference, here’s the ReadParse function (see below). It’s a standard function that’s part of CGI.pm. The way I understand it, I’m not meant to initialize the %in hash (other than satisfying strict) for purposes of setting scope, since the function appears to me to handle that:
sub ReadParse { local(*in); if (@_) { *in = $_[0]; } else { my $pkg = caller(); *in=*{'${pkg}::in'}; } tie(%in,CGI); return scalar(keys %in); } I guess my question is what is the best way to get the %in hash within the context of do()? Thanks again! I hope this is the right way to provide additional info to my original question.
@Dan: I hear ya regarding the &ReadParse syntax. I’d normally use CGI::ReadParse() but in this case I thought it was best to stick to how the CGI.pm documentation has it exactly.
Per the DBI documentation: Binding a tied variable doesn’t work, currently.
DBI is pretty complicated under the hood, and unfortunately goes through some gyrations to be efficient that are causing your problem. I agree with everyone else who says to get rid of the ugly old cgi-lib style code. It’s unpleasant enough to do CGI without a nice framework (go Catalyst), let alone something that’s been obsolete for a decade.