PHP ও MySQL ব্যবহার করে ক্যাটাগরির তালিকা তৈরি

// Category Tree List
function category_tree_list($parent_id = 0, $cat_list = '') {
	global $pdo;
	$sql = "SELECT * FROM categories WHERE parent_id = :parent_id ORDER BY category";
	$stmt = $pdo->prepare($sql);
	$stmt->bindParam(":parent_id", $parent_id, PDO::PARAM_INT);
	$stmt->execute();

	if($stmt->rowCount() > 0){
		
		$class = ($parent_id == 0) ? 'cat-list' : 'sub-cat';
		$cat_list .= "<ul class='$class'>";
		
		while($cat = $stmt->fetch(PDO::FETCH_ASSOC)){
			$cat_list .= "<li>$cat[category]";
			$cat_list = category_tree_list($cat['id'], $cat_list);
			$cat_list .= "</li>";
		}
		
		$cat_list .= "</ul>";
	}
	
	return $cat_list;
}

// Get all Categories from Database
function get_categories_from_db(){
	
	global $pdo;
	$sql = "SELECT * FROM categories ORDER BY category";
	$stmt = $pdo->prepare($sql);
	$stmt->execute();
	
	if ($stmt->rowCount() > 0) {
		$result = $stmt->fetchAll(PDO::FETCH_ASSOC);
		return $result;
	}
	
	return false;
}

// Category Tree List
function category_tree_list($parent_id = 0, $cat_list='', $cat_array=array(), $parent_ids=array()) {
	
	// For the first time, fetch categories from database
	if(empty($cat_array)) {
		$cat_array = get_categories_from_db();
	}
	
	// No category found in Database
	if(empty($cat_array)) {
		return $cat_list;
	}
	
	// Extract Unique Parent IDs
	if (empty($parent_ids)) {
		$parent_ids = array_column($cat_array, 'parent_id');
		$parent_ids = array_unique($parent_ids);
	}
	
	// In case of last-level sub-category item (which has no child item), don't proceed
	// Otherwise, empty "<ul class='sub-cat'></ul>" will be generated
	if(array_search($parent_id, $parent_ids) !==false) {
		$class = ($parent_id == 0) ? 'cat-list' : 'sub-cat';
		$cat_list .= "<ul class='$class'>";
	
		foreach($cat_array as $cat) {
			if($parent_id == $cat['parent_id']) {
				$cat_list .= "<li>$cat[category]";
				$cat_list = category_tree_list($cat['id'], $cat_list, $cat_array, $parent_ids);
				$cat_list .= "</li>";
			}
		}
		
		$cat_list .= "</ul>";
	}
	
	return $cat_list;
}

// For the first time, fetch categories from database
// If DB has no category, then skip to the end
if(empty($cat_array) && $cat_array = get_categories_from_db()) {

	// Extract Unique Parent IDs
	$parent_ids = array_column($cat_array, 'parent_id');
	$parent_ids = array_unique($parent_ids);
}

<ul class='cat-list'>
	<li>
		জীবজগৎ
		<ul class='sub-cat'>
			<li>উদ্ভিদজগৎ</li>
			<li>
				প্রাণিজগৎ
				<ul class='sub-cat'>
					<li>পশু</li>
					<li>পাখি</li>
					<li>মাছ</li>
				</ul>
			</li>
		</ul>
	</li>
	<li>
		জড়জগৎ
		<ul class='sub-cat'>
			<li>আসবাবপত্র</li>
			<li>পানি</li>
			<li>মাটি</li>
		</ul>
	</li>
</ul>