How to use unlimited classification function in PHP development

With the rapid development of the Internet, the functions and requirements of websites are becoming more and more complex. Among them, the unlimited classification function is a very important way to organize and manage information. It can help developers organize information effectively so that users can find what they need more quickly. Today, we will introduce how to use the unlimited classification function in PHP development.

What is the unlimited classification function

In traditional classification, each classification can only have one parent classification and multiple child classifications. However, in some complex scenarios, this classification method will be limited. For example, a product may belong to multiple brands, multiple classification groups, multiple regions, and so on. At this time, the unlimited classification function can provide better solutions.

The unlimited classification function, as the name suggests, has no level restrictions. Classifications can be freely combined, and one piece of data can belong to multiple classifications. This function is suitable for scenarios that require flexible organization of data, such as blog classification, product classification, news classification, etc.

How to implement unlimited classification function

Below, we will step by step introduce how to implement unlimited classification function in PHP development.

Step 1: Create a database table

When creating a database table, we need to consider three key fields, namely classification ID, classification name and classification parent ID. The category ID is the unique identifier of each category, the category name is used to display category information, and the category parent ID indicates the parent category ID of the category.

CREATE TABLE categories (
id int(11) NOT NULL,
name varchar(100) NOT NULL,
parent_id int(11) NOT NULL,
PRIMARY KEY (id)
);

Step 2: Insert classified data

When inserting categorical data into a database table, you can use the nested set model, that is, use left and right values ​​to describe the organizational relationship of each category level. The example is as follows:

INSERT INTO categories (id, name, parent_id, lft, rgt) VALUES
(1 , 'Electrical appliances', 0, 1, 10),
(2, 'TV', 1, 2, 3),
(3, 'Mobile appliances', 1, 4, 9),
(4, 'smartphone', 3, 5, 6),
(5, 'feature phone', 3, 7, 8);

Among them, lft and rgt describe the differences between categories For hierarchical relationships, subcategories and parent categories can be queried recursively.

Step 3: Query classified data

When querying classified data, we can use recursive query. The example is as follows:

function getCategories($parentId = 0 , $level = 0)
{

$sql = 'SELECT * FROM `categories` WHERE `parent_id` = ? ORDER BY `lft` ASC';
$stmt = $pdo->prepare($sql);
$stmt->execute([$parentId]);
$categories = $stmt->fetchAll(PDO::FETCH_ASSOC);

if (!empty($categories)) {
    $level++;
    $categories = array_map(function ($category) use ($level) {
        $category['level'] = $level;
        $category['children'] = getCategories($category['id'], $level);
        return $category;
    }, $categories);
}

return $categories;

}

In this function, we first query all subcategories under the current parent category and sort them by lvalue. Then, by calling itself recursively, the subcategory of the subcategory is queried and saved in the children field. Finally, a categorical array is returned.

Step 4: Display classified data

When displaying classified data, we can use recursive traversal. The example is as follows:

function showCategories($categories)
{

if (!empty($categories)) {
    echo '<ul>';
    foreach ($categories as $category) {
        echo '<li>' . $category['name'] . '</li>';
        if (!empty($category['children'])) {
            showCategories($category['children']);
        }
    }
    echo '</ul>';
}

}

In this function, we first determine whether the category array is empty. If not, then traverse the array and display the category name. Then, if the category has subcategories, call itself recursively to display the subcategories.

Conclusion

Through the above four steps, we can easily implement unlimited classification functions, and can also use recursive methods to display classified data. This function is very common in actual development, especially in e-commerce, news, blogs and other scenarios. I hope this article can inspire PHP developers and help them better cope with actual development needs.

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