Posted by Greg Schnippel on 11/14/05 15:46

I have a large data tree that I wanted to display in an outline
format. I used a textbook tree recursion function to go through the
data and display it as nested unordered lists:

function outputTree($id) {

if (checkChildObjectExists($id)) {
print "<ul>";
$child = getChildArray($id);
foreach ($child as $key => $value) {
print "<li><a href=\"/object/$key/\">$value</a></li>";
outputTree($key);
}
print "</ul>";
}
}

This works as expected:

> Level 1 (Top)
> Level 2
> Level 3 (Bottom)

However, I also want to display a reverse tree to allow users to trace
their way back up the tree after landing on a lower branch. I tried to
be clever and reverse the function above as:

function outputReverseTree($id) {

if (checkParentExists($id)) {
print "<ul>";
$parent = getParentArray($id);
foreach ($parent as $key => $value) {
print "<li><a href=\"/object/$key/\">$value</a>\n";
outputReverseTree($key);
}
print "</ul>";
}
}

Which works, but there is something wrong with my logic as the tree
comes back reversed:

> Level 3 (Bottom)
> Level 2
> Level 1 (Top)

Any suggestions on how to do this?

Thanks,

- Greg

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