Foreach - recursion? - php

Question

I have this code that is getting all categories and subcategories from a woocommerce based website in a hierarchical order, and it works but each and every time when I want to add a new level of depth
category
->sub-cat
->sub-sub-cat
->sub-sub-sub-cat
->etc
I have to add one more foreach loop inside the last loop (I'm not even sure if you can understand me to cause honestly I don't even know how to explain this - sorry, please be patient, it is my second month in PHPs 'fields')
So, I'm trying to get rid of all those foreach loops (to make it more dynamic) and I heard that there is a way to do that by using something called recursion, the kind of stuff that I can use to make this happen. I don't really understand how that works and I've read like the whole day about it so if there is somebody who can help me understand how to get this done I'll be happy?
Here is my code, part of it is taken from StackOverflow.
<ul>
<?php
$taxonomy = 'product_cat';
$orderby = 'name';
$hierarchical = 1;
$args = array(
'taxonomy' => $taxonomy,
'orderby' => $orderby,
'hierarchical' => $hierarchical
);
$cat = get_categories( $args );
foreach ($cat as $c) {
if($c->category_parent == 0) {
$catID = $c->term_id;
echo '<li>'. $c->name .'';
$args = array(
'taxonomy' => $taxonomy,
'parent' => $catID,
'orderby' => $orderby,
'hierarchical' => $hierarchical
);
$cat = get_categories( $args );
if($cat) {
echo '<ul>';
foreach($cat as $c) {
$catID = $c->term_id;
echo '<li>'. $c->name , apply_filters( 'woocommerce_subcategory_count_html', ' (' . $c->count . ')', $category ) .'';
$args = array(
'taxonomy' => $taxonomy,
'parent' => $catID,
'orderby' => $orderby,
'hierarchical' => $hierarchical
);
$cat = get_categories( $args );
if($cat){
echo '<ul>';
foreach ($cat as $c) {
$catID = $c->term_id;
echo '<li>'. $c->name , apply_filters( 'woocommerce_subcategory_count_html', ' (' . $c->count . ')', $category ) .'';
$args = array(
'taxonomy' => $taxonomy,
'parent' => $catID,
'orderby' => $orderby,
'hierarchical' => $hierarchical
);
$cat = get_categories( $args );
if($cat){
echo '<ul>';
foreach ($cat as $c) {
$catID = $c->term_id;
echo '<li>'. $c->name , apply_filters( 'woocommerce_subcategory_count_html', ' (' . $c->count . ')', $category ) .'</li>';
}
echo '</ul>';
}
echo '</li>';
}
echo '</ul>';
}
echo '</li>';
}
echo '</ul>';
}
echo '</li>';
}
}
?>
It works perfectly, though I'm aware that it is not too smart, so please don't be too harsh on me.

Answer 1

Here is an example of recursion:
You create a function that looks at the item of the array if it's an array you call the function again and pass the item to it (the subarray).
If it's not an array you echo it.
$arr = [1,2,3,[4,5,[6]]];
print_items($arr);
Function print_items($arr){
Foreach($arr as $item){
If(is_array($item)){
print_items($item);
}Else{
Echo $item;
}
}
}
https://3v4l.org/vbjaO

Answer 2

A WordPress-specific printing function might look like this:
<?php
function display_child_categories_of($category_id) {
$subcategories = get_categories(array('child_of' => category_id));
foreach ($subcategories as $subcategory) {
echo '<li>';
echo $subcategory->name;
echo '<ul class="children">';
display_child_categories_of($subcategory);
echo '</ul>';
echo '</li>';
}
}
?>
<ul>
<?php
display_child_categories_of(0); // gets all top-level categories
?>
</ul>
This is a barebones version; you'll want to add in the additional parameters you're using to the get_categories() arguments and then tweak the HTML as needed.
However, as #jaswrks mentioned in the comments, you should use the built-in walk_category_tree() WordPress function instead if it works for your situation.