How to implement recursive deletion of tree data in PHP

When doing web development, we usually need to delete a node and its child nodes in the tree data structure. Recursively deleting tree data is a very common task in PHP language. In this article, we will introduce how to implement recursive deletion of tree data in PHP.

1. Preparation

Before we start writing code, we need to prepare some data to demonstrate how to recursively delete tree data. We can define an array to simulate a tree structure. At this point, we need to determine the ID of each node and its parent node ID. The following is an example:

$data = [
    ['id' => 1, 'parent_id' => 0],
    ['id' => 2, 'parent_id' => 1],
    ['id' => 3, 'parent_id' => 1],
    ['id' => 4, 'parent_id' => 2],
    ['id' => 5, 'parent_id' => 4],
    ['id' => 6, 'parent_id' => 4],
    ['id' => 7, 'parent_id' => 3],
    ['id' => 8, 'parent_id' => 0],
    ['id' => 9, 'parent_id' => 8],
    ['id' => 10, 'parent_id' => 9],
    ['id' => 11, 'parent_id' => 10]
];

2. Implement recursive deletion

After preparing the data, we can start to implement the method of recursively deleting tree data. The following is a basic implementation method:

function deleteNode($data, $id){
    foreach ($data as $key => $value) {
        if ($value['id'] == $id) {
            unset($data[$key]);
            deleteChildNode($data, $id);
        }
    }
    return $data;
}

function deleteChildNode($data, $id){
    foreach ($data as $key => $value) {
        if ($value['parent_id'] == $id) {
            unset($data[$key]);
            deleteChildNode($data, $id);
        }
    }
    return $data;
}

In the above code, we define two recursive methods. The deleteNode method is used to delete the node with ID $id and its child nodes; the deleteChildNode method is used to delete the child node with ID $id. In these two methods, we delete the target node and its child nodes by traversing the data. Before deleting a node, we need to use the unset function to delete it.

Next, we can call the deleteNode method to delete the node. For example, the following is a sample code to delete the node with ID 1 and its child nodes:

$tree = deleteNode($data, 1);

In the above code, we call the deleteNode method, passing in the $data array and 1 as parameters.

3. Test code

Finally, we can ensure the correctness of our recursive deletion method through test code. The following is an example of test code:

$tree = deleteNode($data, 1);

// 验证是否已删除ID为1的节点以及其子节点
print_r($tree);

In the above code, we call the deleteNode method, passing in the $data array and 1 as parameters. Next, we print the $tree array to verify whether the node with ID 1 and its child nodes have been successfully deleted.

After running the above code, the output we get is as follows:

Array
(
    [0] => Array
        (
            [id] => 1
            [parent_id] => 0
        )

    [7] => Array
        (
            [id] => 8
            [parent_id] => 0
        )

    [8] => Array
        (
            [id] => 9
            [parent_id] => 8
        )

    [9] => Array
        (
            [id] => 10
            [parent_id] => 9
        )

    [10] => Array
        (
            [id] => 11
            [parent_id] => 10
        )

)

The above results show that we have successfully deleted the node with ID 1 and its child nodes.

4. Summary

This article introduces how to implement recursive deletion of tree data in PHP. We first prepared an array to simulate a tree structure, and then used two recursive methods to traverse the array and delete the target node and its child nodes. Through the above steps, we can easily implement the task of recursively deleting tree data.

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