How to create a hierarchical list from data - php

Question

With PHP, I need to create a three-level-deep navbar. I have data like this:
And I need it to be organized like so:
Napkins
--Colored Napkins
----American Tradition
--White Beverage Napkins
----American Digital
----American Tradition
----American Hi-Speed
--White Luncheon Napkins
----American Digital
----American Tradition
----American Hi-Speed
--White Dinner Napkins
...(etc)...
Plates
--Eco-Plates
----American Tradition
--Plastic Trays
...(etc)...
Just using a relatively simple <ul> structure with <li> and <a>. Clearly a loop is needed to go through the rows of data. And I know that I'd need to do lots of "testing" to see if the "current" category/subcategory/method matches the one from the previous iteration of the loop.
But I'm having trouble getting the <ul> and <li> tags to close at the correct locations and to not show the print method tier when there is only one print method for a given category/subcategory. Or when there is no print method (sometimes it can be null, such as for plastic utensils). How can I set this up?
Edit
The code I have so far, which almost works, but is very clunky ($items is the data from the database):
function addMethodMenuItem($result, $short_cat_name, $short_subcat_name, $short_method_name, $this_method_name)
{
$result .= "<li>";
$result .= "<a";
$result .= " href=\"product.php?category={$short_cat_name}&subcategory={$short_subcat_name}&printMethod={$short_method_name}\"";
$result .= " target=\"_self\"";
$result .= " title=\"{$this_method_name}\">";
$result .= $this_method_name;
$result .= "</a>";
$result .= "</li>";
return $result;
}
function addSubMenuItem($item, $previous_cat_name, $previous_subcat_name, $result, $newCat)
{
$this_cat_name = $item["category_name"];
$this_subcat_name = $item["subcategory_name"];
$this_method_name = $item["method_name"];
$short_cat_name = $item["category_short"];
$short_subcat_name = $item["subcategory_short"];
$short_method_name = $item["method_short"];
if ($this_subcat_name != $previous_subcat_name || $this_cat_name != $previous_cat_name) { // We have to create a new "subcategory" menu item
if ($previous_subcat_name != null && !$newCat) { // if this isn't the first subcategory menu item of the category.
$result .= "</ul></li>";
}
$result .= "<li>";
$result .= "<a class=\"ajxsub\"";
$result .= " href=\"#\">";
$result .= $this_subcat_name;
$result .= "</a>";
$result .= "<ul>";
}
$result = addMethodMenuItem($result, $short_cat_name, $short_subcat_name, $short_method_name, $this_method_name);
return $result;
}
function printMenu(array $items, $previous_cat_name, $result)
{
// $result .= "<ul>";
$previous_subcat_name = null;
foreach ($items as $item) {
$newCat = false;
$this_cat_name = $item["category_name"];
$this_subcat_name = $item["subcategory_name"];
if ($this_cat_name != $previous_cat_name) {
if ($previous_cat_name != null) { // if this isn't the very first top-level menu item.
$result .= "</ul></li>";
$result .= "</ul></li>";
$newCat = true;
}
$result .= "<li>";
$result .= "<a class=\"ajxsub\"";
$result .= " href=\"#\">";
$result .= $this_cat_name;
$result .= "</a>";
$result .= "<ul>";
}
$result = addSubMenuItem($item, $previous_cat_name, $previous_subcat_name, $result, $newCat);
$previous_subcat_name = $this_subcat_name;
$previous_cat_name = $this_cat_name;
}
$result .= "</ul></li>";
// $result .= "</ul>";
return $result;
}

Answer 1

Give this a whirl - assumes you have the data already sorted (else sort it first):
$flds = ['category_name', 'subcategory_name', 'method_name'];
$lval = ['it will never be this'];
$result = "";
$start = true;
foreach ($items as $item) {
if ($start) {
$result .= "<ul>";
$first = $start = false;
} else $first = true;
foreach ($flds as $k=>$val) {
if ($item[$val] != $lval[$k]) {
$result .= genhtml($k, $item[$val], $first);
$first = false;
$lval[$k] = $item[$val];
$lval[$k+1] = ''; // Don't care if this goes over the max
}
}
}
if (!$start) $result .= "</ul></li></ul></li></ul>\n";
echo $result;
function genhtml($level, $value, $first) {
switch ($level) {
case 0:
$close = $first ? "</ul></li></ul></li>" : "";
return "{$close}<li>{$value}<ul>\n";
case 1:
$close = $first ? "</ul></li>" : "";
return " {$close}<li>{$value}<ul>\n";
case 2:
return " <li>{$value}</li>\n";
default:
throw new Exception("I don't know how to do '{$level}'");
}
}
The code above (with some of your data) produces:
<ul><li>Napkins<ul>
<li>Colored Napkins<ul>
<li>American Tradition</li>
</ul></li><li>White Beverage Napkins<ul>
<li>American Digital</li>
<li>American Tradition</li>
<li>American Hi Speed</li>
</ul></li><li>White Luncheon Napkins<ul>
<li>American Digital</li>
<li>American Tradition</li>
<li>American Hi Speed</li>
</ul></li><li>White Dinner Napkins<ul>
<li>American Digital</li>
<li>American Tradition</li>
<li>American Hi Speed</li>
</ul></li></ul></li><li>Plates<ul>
<li>Eco Plates<ul>
<li>American Tradition</li>
</ul></li></ul></li></ul>
(Not pretty, but I think its right).
Also will ignore duplicate records (maybe not what you want?). If you need other data from your record to produce the html, pass $item to genhtml as well.