Amateur trying to fix dropdown menu from SQL - php

Question

I'm trying to help a friend with a website. I usually don't work with PHP, jquery.
The dropdown has 4 levels. The first level has 4 points. The 4 points have their own sub-levels, different for each other.
I'm trying to find them and then make them display in a dropdown, directly from the database.
And I'm stuck at the second level, with this error
Notice: Trying to get property 'subcategorie' of non-object in .....
What I've managed to do, until now:
<?php $categorii = $wpdb->get_results("SELECT DISTINCT categorie FROM catalog_rural");
?>
<?php
$subcategorie = $wpdb->get_results("SELECT DISTINCT subcategorie FROM catalog_rural WHERE categorie = 'Afaceri'");
?>
<div class="container">
<?php
foreach($categorii as $categorie) {
?>
<ul>
<li>
<a <?php if(isset($_GET['categorie']) && $categorie->categorie==$_GET['categorie']){ echo "btn-success";}else{ echo "btn-info";};?> href="<?php site_url(); ?>catalog-rural/?categorie=<?php echo urlencode($categorie->categorie); ?>"> <i class="fa fa-caret-down"></i>
<?php echo $categorie->categorie ; ?> </a>
<ul class="">
<li> <?php echo $subcategorie->subcategorie; ?>
</li>
</ul>
</li>
</ul>
</a>

Answer 1

Hi You need to do a foreach loop for $subcategorieas you did for $categorii. Because you are getting an array and not a object as you got for $categorii. Here I set it around the li because it seems to be the best.
<?php
$categorii = $wpdb->get_results("SELECT DISTINCT categorie FROM catalog_rural");
?>
<?php
$subcategories = $wpdb->get_results("SELECT DISTINCT subcategorie FROM catalog_rural WHERE categorie = 'Afaceri'");
?>
<div class="container">
<?php
foreach( $categorii as $categorie ) {
?>
<ul>
<li>
<a
<?php
#### What are these? Are they classnames? ####
if( isset( $_GET['categorie'] ) && $categorie->categorie==$_GET['categorie'] ){
echo "btn-success";
}else{
echo "btn-info";
};
?> href="<?php site_url(); ?>catalog-rural/?categorie=<?php echo urlencode( $categorie->categorie ); ?>">
<i class="fa fa-caret-down"></i>
<?php echo $categorie->categorie; ?>
</a>
<ul class="">
<?php foreach( $subcategories as $subcategorie ) { ?>
<li>
<a href="<?php echo site_url(); ?>/catalog-rural/?categorie=<?php echo urlencode( $_GET['categorie'] ); ?>&subcategorie=<?php echo $subcategorie->subcategorie; ?>" class="list-group-item <?php if($subcategorie->subcategorie==$_GET['subcategorie']){ echo "active";};?> ">
<?php echo $subcategorie->subcategorie; ?>
</a>
</li>
<?php } ?>
</ul>
</li>
</ul>

Answer 2

Not intended as a solution to your error " Trying to get property 'subcategorie' of non-object" ~ just to illustrate the invalid markup. If you use proper code indentation you would probably have been able to spot this!
<?php
$categorii = $wpdb->get_results("SELECT DISTINCT categorie FROM catalog_rural");
?>
<?php
$subcategorie = $wpdb->get_results("SELECT DISTINCT subcategorie FROM catalog_rural WHERE categorie = 'Afaceri'");
?>
<div class="container">
<?php
foreach( $categorii as $categorie ) {
?>
<ul>
<li>
<a
<?php
#### What are these? Are they classnames? ####
if( isset( $_GET['categorie'] ) && $categorie->categorie==$_GET['categorie'] ){
echo "btn-success";
}else{
echo "btn-info";
};
?> href="<?php site_url(); ?>catalog-rural/?categorie=<?php echo urlencode( $categorie->categorie ); ?>">
<i class="fa fa-caret-down"></i>
<?php echo $categorie->categorie; ?>
</a>
<ul class="">
<!-- ### Where is the opening LI? ### -->
<a href="<?php echo site_url(); ?>/catalog-rural/?categorie=<?php echo urlencode( $_GET['categorie'] ); ?>&subcategorie=<?php echo $subcategorie->subcategorie; ?>" class="list-group-item <?php if($subcategorie->subcategorie==$_GET['subcategorie']){ echo "active";};?> ">
<?php echo $subcategorie->subcategorie; ?>
</a>
</li>
</ul>
</li>
</ul>
</a><!-- ### what is this closing? ### -->