TABLE_STUFF
~~~~~~~~~~~~~~~~~~~~
ID (pk)
name
parent_ID

##</code><code>##

TABLE_STUFF
~~~~~~~~~~~~~~~~~~~~
ID (pk)
name
parent_ID
lft
rght
depth
lineage

##</code><code>##

sub rebuild_tree
{
	my $dbh = shift;
	my $dir_ID = shift;
	my $left = shift;

	my $right = $left + 1;

	my $sql = "select ID, name from DIRECTORIES where parent_ID = ?";
	my $sth = $dbh->prepare($sql);

	$sth->execute($dir_ID) || return $right + 1;

	my $row;
	while($row = $sth->fetchrow_arrayref)
	{
		#print STDERR "Processing: ", $row->[0], " with name: ", $row->[1],"\n";
		$right = rebuild_tree($dbh, $row->[0], $right);
	}

	my $sql2 = "update DIRECTORIES set lft = ?, rght = ? where ID = ?";
	my $sth2 = $dbh->prepare($sql2);
	$sth2->execute($left, $right, $dir_ID);
	return $right + 1;
}

##</code><code>##

use vars qw($sth);
....

# And then in the function
$sth || = $dbh->prepare($sql);

##</code><code>##

DBD::mysql::st fetchrow_arrayref failed: fetch() without execute()