Question

So, I’m new to Perl. I’m attempting to create a recursive subroutine. The logic seems simple:

sub directory_tree
{
    my $sth = $dbh->prepare("
        SELECT id, org_id, name
        FROM media_directories
        WHERE
            org_id = ?
            AND parent = ?
            AND bucket = ?
    ");
    $sth->bind_param(1, $_[0]);
    $sth->bind_param(2, $_[1]);
    $sth->bind_param(3, 'mfsermons.myflock2.com');
    $sth->execute;

    $result = '';
    while(my($id, $org_id, $name) = $sth->fetchrow_array())
    {
        $result .= "<option value='$id'>$name</option>";  #377
        $result .= directory_tree($org_id, $id);          #378
    }

    return $result;
}

$directory_tree = '<select name="folder">';
$directory_tree .= directory_tree($churchid, 0);
$directory_tree .= '</select>';

---

Why is it that when I print $result after line 377 that it is equal to the expected value, but when I print it on line 378, nothing appears? Shouldn’t the .= operator just run the function again, and then append to the value?

My best guess is that there are some scope issues in Perl I don’t understand, particularly with regards to $result. However, for the life of me, I can’t figure out what’s wrong, and I have absolutely no idea where to look!

When I turn on error reporting, fatals and warnings, nothing is returned. What could possibly be going wrong that I’m missing?

Answer 1

use strict, avoid global variables. In other words: you are reusing the global $result, resetting its value in each call to the subroutine.