Add vendor to favourite

<?php

		// Get a db connection.
		$db = JFactory::getDbo();
		
		// Create a new query object.
		$query = $db->getQuery(true);
		
		$query->select('vendor_id');
		$query->from($db->quoteName('tbuonapp_hikamarket_vendor'));
		$query->where('vendor_name = ' . '"' . $this->row->category_name . '"');

		// Reset the query using our newly populated query object.
		$db->setQuery($query);
		$idVendor = $db->loadResult();
		
		
		// Get a db connection.
		$db = JFactory::getDbo();
		
		// Create a new query object.
		$query = $db->getQuery(true);
		
		$query->select('vendor_alias');
		$query->from($db->quoteName('tbuonapp_hikamarket_vendor'));
		$query->where('vendor_name = ' . '"' . $this->row->category_name . '"');

		// Reset the query using our newly populated query object.
		$db->setQuery($query);
		$aliasVendor = $db->loadResult();
		
	?>

<?php if($idVendor != null and $idVendor != ""){ ?>
		<br>
		
		<form method="post">
			<div>
				<?php 
					foreach ($users as $currentUser) {
						if($currentUser == $user->username) {
							$favourite = true;
						}elseif($favourite != true){
							$favourite = false;
						}
					}
				?>
				<?php if($favourite){ ?>
					
					<input class ='hikabtn hikawishlist' value="Togli dai preferiti" name="<?php echo 'removeFavourite' . $this->row->category_id; ?>" type="submit">
				
				<?php }else{ ?>
				
					<input class ='hikabtn hikawishlist' value="Aggiungi ai preferiti" name="<?php echo 'favourite' . $this->row->category_id; ?>" type="submit">
				
				<?php } ?>
			</div>
			
			<?php
				if(isset($_POST['removeFavourite' . $this->row->category_id])){
				
					for($i = 0; $i < count($users) - 1; $i++) {
						if($users[$i] != $user->username) {
							$stringUsernamesFavourites .= $users[$i] . ";";
						}
					}
					
				}elseif(isset($_POST['favourite' . $this->row->category_id])){
					$stringUsernamesFavourites = $usersFavourites . $user->username . ";";
				}
			
				if(isset($_POST['favourite' . $this->row->category_id]) or isset($_POST['removeFavourite' . $this->row->category_id])){
					
					// Get a db connection.
					$db = JFactory::getDbo();
					
					// Create a new query object.
					$query = $db->getQuery(true);
					
					// Campi da modificare
					$fields = array(
						$db->quoteName('utenti_preferiti') . ' = "' . $stringUsernamesFavourites . '"'
					);
					
					// Preparazione della query
					$query->update($db->quoteName('tbuonapp_hikashop_category'));
					$query->set($fields);
					$query->where('category_id = ' . '"' . $this->row->category_id . '"');
					
					// Impostazione ed esequzione della query precedentemente impostata
					$db->setQuery($query);
					$db->execute();
					
					header('Location: https://www.buonapp.ch/ristoranti');
				}
			?>
		</form>
	<?php } ?>