1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
|
---
layout: default
title: Abstract Syntax Tree
description: Using the Abstract Syntax Tree (AST) to manipulate the parsed content
---
# Abstract Syntax Tree
This library uses a doubly-linked list Abstract Syntax Tree (AST) to represent the parsed block and inline elements. All such elements extend from the `Node` class.
## `Document`
The root node of the AST will always be a `Document` object. You can obtain this node a few different ways:
- By calling the `parse()` method on the `DocParser`
- By calling the `getDocument()` method on either the `DocumentPreParsedEvent` or `DocumentParsedEvent` (see the [Event Dispatcher documentation](/1.6/customization/event-dispatcher/))
## Traversal
The following methods can be used to traverse the AST:
- `previous()`
- `next()`
- `parent()`
- `firstChild()`
- `lastChild()`
- `children()`
## Iteration / Walking the Tree
If you'd like to iterate through all the nodes, use the `walker()` method to obtain an instance of `NodeWalker`. This will walk through the entire tree, emitting `NodeWalkerEvent`s along the way.
```php
use League\CommonMark\Node\NodeWalker;
/** @var NodeWalker $walker */
$walker = $document->walker();
while ($event = $walker->next()) {
echo 'I am ' . ($event->isEntering() ? 'entering' : 'leaving') . ' a ' . get_class($event->getNode()) . ' node' . "\n";
}
```
This walker doesn't use recursion, so you won't blow the stack when working with deeply-nested nodes.
## Modification
The following methods can be used to modify the AST:
- `insertAfter(Node $sibling)`
- `insertBefore(Node $sibling)`
- `replaceWith(Node $replacement)`
- `detach()`
- `appendChild(Node $child)`
- `prependChild(Node $child)`
- `detachChildren()`
- `replaceChildren(Node[] $children)`
## `DocumentParsedEvent`
The best way to access and manipulate the AST is by adding an [event listener](/1.6/customization/event-dispatcher/) for the `DocumentParsedEvent`.
|
