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Simdom - A simplified and relaxed DOM structure library

Simdom is a lightweight PHP library designed to make parsing and manipulating DOM documents as straightforward as possible. It requires no external dependencies or extensions.

Without using the built-in PHP DOM extension, Simdom can have its own opinionated appraoch on how HTML documents should be parsed and manipulated. It lets you to work with "non-compliant" HTML structure in a literal and intuitive way.

Before outputing the HTML string of the document, you can call the $document->validate() method to ensure that the document is valid according to the HTML5 specification.

Key differences from the standard HTML5 DOM specification / PHP DOM extension

Simplified node types

Simdom provides 6 node types that form the DOM tree:

• Document - The root document node
• Doctype - Document type declarations
• Element - HTML elements with attributes and child nodes
• Text - Text content within elements
• Comment - HTML comments
• Fragment - Document fragments for grouping nodes

Attributes are not considered as a node type in Simdom, but rather as properties of Element nodes.

CDATA section or processing instructions are not supported, as they would not be valid in HTML5 documents.

Simplified and relaxed DOM structure

• There is no concept of an owner document, meaning nodes can be freely moved between documents.
• There is no concept of namespace.
• Document, Element and Fragment nodes can have child nodes of any type except Document and Fragment, in any order, i.e.:
  • Document can hold Text child.
  • Document does not restrict at most one Doctype child, and it does not have to be placed before any Element child.
  • Document does not restrict at most one Element child.
  • Element and Fragment can hold Doctype child.
• There is no concept of valid element structure, meaning elements can be nested in any way, even if it would not be valid HTML5, i.e. <table><ul></ul></table> would be parsed as it is.
• Misaligned end tags are fixed by finding the last matching start tag, i.e. <div><span>abc</div> would be parsed as <div><span>abc</span></div>. If there is no matching start tag, the end tag is ignored.
• <template> elements are treated as a Rawtext type element like <script> or <style>.
• Self-closing tag syntax is supported, for example <div /> is parsed as <div></div>.
• All element names and attributes names are parsed as their ASCII-lowercase form.

Restrictions

However, there are still some lines you cannot cross in Simdom:

• Document and Fragment has no parent node, and cannot be a child of any other node. (Inserting Fragment as a child of any parent node is fine though, as it means inserting the Fragment's child nodes.)
• Element name and attribute names must conform to the HTML5 specification.
• Doctype name, public identifier and system identifier must conform to the HTML5 specification.
• Doctype name must be present if either public or system identifier is present.
• No control characters are allowed anywhere, e.g. you cannot inject an delete character (U+007F) to a Text node.
• Comment cannot contain the character sequence -->.
• If a Text node is under a Rawtext type (e.g. <script>) or Rcdata type (e.g. <textarea>) element, it cannot contain the character sequence which may terminate the corresponding element start tag, e.g. </script, or </textarea.

Getting Started

Installation

Requirements

• PHP 8.4 or higher

Some Basic Usages

Parsing HTML Documents

Node Manipulation

Traversing and Manipulating the DOM Tree

Adding and Removing Nodes

Working with Attributes

Searching and Traversal

HTML Serialization