您如何在 PHP 中解析和处理 HTML/XML?

2022-01-10 00:00:00 xml xml-parsing html-parsing php html

如何解析 HTML/XML 并从中提取信息?

解决方案

Native XML Extensions

我更喜欢使用 原生 XML 扩展，因为它们与PHP，通常比所有 3rd 方库都快，并为我提供对标记的所有控制.

DOM

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DOM 扩展允许您使用 PHP 5 通过 DOM API 对 XML 文档进行操作.它是 W3C 文档对象模型核心级别 3 的实现，一个平台和语言中立的接口，允许程序和脚本动态访问和更新文档的内容、结构和样式.

DOM 能够解析和修改现实世界(损坏的)HTML，它可以执行 XPath 查询.它基于 libxml.

使用 DOM 需要一些时间来提高工作效率，但 IMO 非常值得.由于 DOM 是一个与语言无关的接口，您会发现多种语言的实现，因此如果您需要更改您的编程语言，那么您很可能已经知道如何使用该语言的 DOM API.

如何使用 DOM 扩展已在 StackOverflow 上广泛介绍，因此，如果您选择使用它，您可以确定您遇到的大部分问题都可以通过搜索/浏览 Stack Overflow 来解决.

基本用法示例和常规概念概述可在其他答案中找到.

XMLReader

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XMLReader 扩展是一个 XML 拉式解析器.阅读器充当文档流上的光标，并在途中的每个节点处停止.

XMLReader 和 DOM 一样，都是基于 libxml.我不知道如何触发 HTML 解析器模块，因此使用 XMLReader 解析损坏的 HTML 的机会可能不如使用 DOM 强大，您可以明确告诉它使用 libxml 的 HTML 解析器模块.

基本用法示例可在另一个答案中找到.

XML 解析器

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此扩展允许您创建 XML 解析器，然后为不同的 XML 事件定义处理程序.每个 XML 解析器还有一些可以调整的参数.

XML Parser 库也是基于 libxml，并实现了 SAX 样式的 XML 推送解析器.它可能是比 DOM 或 SimpleXML 更好的内存管理选择，但比 XMLReader 实现的拉式解析器更难使用.

SimpleXml

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SimpleXML 扩展提供了一个非常简单易用的工具集，可以将 XML 转换为可以使用普通属性选择器和数组迭代器处理的对象.

当您知道 HTML 是有效的 XHTML 时，SimpleXML 是一个选项.如果您需要解析损坏的 HTML，甚至不要考虑 SimpleXml，因为它会阻塞.

有基本使用示例，有PHP 手册中有很多其他示例.

第 3 方库(基于 libxml)

如果您更喜欢使用第 3 方库，我建议您使用实际使用 DOM/libxml 下面而不是字符串解析.

FluentDom

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FluentDOM 为 PHP 中的 DOMDocument 提供了一个类似 jQuery 的 fluent XML 接口.选择器是用 XPath 或 CSS 编写的(使用 CSS 到 XPath 转换器).当前版本扩展了 DOM 实现标准接口并添加了 DOM 生活标准的功能.FluentDOM 可以加载 JSON、CSV、JsonML、RabbitFish 等格式.可以通过 Composer 安装.

HtmlPageDom

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Wa72HtmlPageDom 是一个 PHP 库，用于轻松操作 HTML使用 DOM 的文档.它需要来自 Symfony2 的 DomCrawler用于遍历的组件DOM 树并通过添加操作方法来扩展它HTML 文档的 DOM 树.

phpQuery

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phpQuery 是一个基于 jQuery JavaScript 库的服务器端、可链接、CSS3 选择器驱动的文档对象模型 (DOM) API.该库是用 PHP5 编写的，并提供了额外的命令行界面 (CLI).

这被描述为放弃软件和漏洞:使用风险自负"；但似乎维护得很少.

laminas-dom

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LaminasDom 组件(以前称为 Zend_DOM)提供了用于处理 DOM 文档和结构的工具.目前，我们提供 LaminasDomQuery，它为使用 XPath 和 CSS 选择器查询 DOM 文档提供了一个统一的接口.

这个包被认为是功能完整的，现在处于仅安全维护模式.

fDOMDocument

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fDOMDocument 扩展了标准 DOM 以在所有错误情况下使用异常，而不是 PHP 警告或通知.为了方便和简化 DOM 的使用，他们还添加了各种自定义方法和快捷方式.

sabre/xml

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sabre/xml 是一个包装和扩展 XMLReader 和 XMLWriter 类的库，以创建一个简单的xml to object/array".映射系统和设计模式.写入和读取 XML 是一次性的，因此速度很快，并且在大型 xml 文件上需要的内存较少.

FluidXML

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FluidXML 是一个 PHP 库，用于使用简洁流畅的 API 操作 XML.它利用 XPath 和流畅的编程模式变得有趣且有效.

第 3 方(不基于 libxml)

基于 DOM/libxml 构建的好处是您可以立即获得良好的性能，因为您是基于本机扩展的.然而，并不是所有的第 3 方库都走这条路.下面列出了其中一些

PHP 简单 HTML DOM 解析器

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  • 用 PHP5+ 编写的 HTML DOM 解析器让您以非常简单的方式操作 HTML！
  • 需要 PHP 5+.
  • 支持无效的 HTML.
  • 使用类似于 jQuery 的选择器在 HTML 页面上查找标签.
  • 在一行中从 HTML 中提取内容.

我一般不推荐这个解析器.代码库很糟糕，解析器本身相当慢且内存不足.并非所有的 jQuery 选择器(例如 子选择器)都是可能的.任何基于 libxml 的库都应该轻松胜过这一点.

PHP Html 解析器

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PHPHtmlParser 是一个简单、灵活的 html 解析器，它允许您使用任何 css 选择器(如 jQuery)来选择标签.目标是协助开发需要快速、简单的方法来抓取 html 的工具，无论它是否有效！这个项目最初是由 sunra/php-simple-html-dom-parser 支持的，但支持似乎已经停止，所以这个项目是我对他以前工作的改编.

同样，我不推荐这个解析器.由于 CPU 使用率很高，所以速度相当慢.也没有清除已创建 DOM 对象内存的功能.这些问题特别适用于嵌套循环.文档本身不准确且拼写错误，自 2016 年 4 月 14 日起对修复没有任何回应.

HTML 5

您可以使用上述方法来解析 HTML5，但由于 HTML5 允许的标记，可能会有一些怪癖.因此，对于 HTML5，您可能需要考虑使用专用解析器.请注意，这些是用 PHP 编写的，因此与使用低级语言编译的扩展相比，性能较慢且内存使用量增加.

HTML5DomDocument

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HTML5DOMDocument 扩展了本机 DOMDocument 库.它修复了一些错误并添加了一些新功能.

  • 保留 html 实体(DOMDocument 不保留)
  • 保留 void 标签(DOMDocument 不保留)
  • 允许插入将正确部分移动到适当位置的 HTML 代码(头部元素插入头部，主体元素插入正文)
  • 允许使用 CSS 选择器查询 DOM(当前可用:*、tagname、tagname#id、#id, tagname.classname, .classname, tagname.classname.classname2, .classname.classname2, <代码>标签名[属性选择器], [属性选择器], div, p, div p, div > p、div + p 和 p ~ ul.)
  • 添加对 element->classList 的支持.
  • 添加对 element->innerHTML 的支持.
  • 添加对 element->outerHTML 的支持.

HTML5

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HTML5 是完全用 PHP 编写的符合标准的 HTML5 解析器和编写器.它很稳定，并在许多生产网站中使用，下载量超过 500 万次.

HTML5 提供以下功能.

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  • HTML5 序列化器
  • 支持 PHP 命名空间
  • 作曲家支持
  • 基于事件(类似 SAX)的解析器
  • DOM 树构建器
  • 与 QueryPath 的互操作性
  • 在 PHP 5.3.0 或更高版本上运行

正则表达式

最后也是最不推荐的，您可以使用 正则表达式从 HTML 中提取数据一个>.通常不鼓励在 HTML 上使用正则表达式.

您在网络上找到的大多数与标记匹配的片段都很脆弱.在大多数情况下，它们只适用于非常特殊的 HTML 片段.微小的标记更改，例如在某处添加空格，或添加或更改标记中的属性，可能会使 RegEx 在编写不正确时失败.在 HTML 上使用 RegEx 之前，您应该知道自己在做什么.

HTML 解析器已经知道 HTML 的语法规则.必须为您编写的每个新 RegEx 教授正则表达式.正则表达式在某些情况下很好，但这实际上取决于您的用例.

您可以编写更可靠的解析器，但是使用正则表达式编写一个完整且可靠的自定义解析器当上述库已经存在并且在这方面做得更好时，这是浪费时间.

另请参阅Cthulhu 方式解析 Html

书籍

如果你想花点钱，看看

  • PHP 架构师使用 PHP 进行网页抓取的指南

我不隶属于 PHP Architect 或作者.

How can one parse HTML/XML and extract information from it?

解决方案

Native XML Extensions

I prefer using one of the native XML extensions since they come bundled with PHP, are usually faster than all the 3rd party libs and give me all the control I need over the markup.

DOM

The DOM extension allows you to operate on XML documents through the DOM API with PHP 5. It is an implementation of the W3C's Document Object Model Core Level 3, a platform- and language-neutral interface that allows programs and scripts to dynamically access and update the content, structure and style of documents.

DOM is capable of parsing and modifying real world (broken) HTML and it can do XPath queries. It is based on libxml.

It takes some time to get productive with DOM, but that time is well worth it IMO. Since DOM is a language-agnostic interface, you'll find implementations in many languages, so if you need to change your programming language, chances are you will already know how to use that language's DOM API then.

How to use the DOM extension has been covered extensively on StackOverflow, so if you choose to use it, you can be sure most of the issues you run into can be solved by searching/browsing Stack Overflow.

A basic usage example and a general conceptual overview are available in other answers.

XMLReader

The XMLReader extension is an XML pull parser. The reader acts as a cursor going forward on the document stream and stopping at each node on the way.

XMLReader, like DOM, is based on libxml. I am not aware of how to trigger the HTML Parser Module, so chances are using XMLReader for parsing broken HTML might be less robust than using DOM where you can explicitly tell it to use libxml's HTML Parser Module.

A basic usage example is available in another answer.

XML Parser

This extension lets you create XML parsers and then define handlers for different XML events. Each XML parser also has a few parameters you can adjust.

The XML Parser library is also based on libxml, and implements a SAX style XML push parser. It may be a better choice for memory management than DOM or SimpleXML, but will be more difficult to work with than the pull parser implemented by XMLReader.

SimpleXml

The SimpleXML extension provides a very simple and easily usable toolset to convert XML to an object that can be processed with normal property selectors and array iterators.

SimpleXML is an option when you know the HTML is valid XHTML. If you need to parse broken HTML, don't even consider SimpleXml because it will choke.

A basic usage example is available, and there are lots of additional examples in the PHP Manual.

3rd Party Libraries (libxml based)

If you prefer to use a 3rd-party lib, I'd suggest using a lib that actually uses DOM/libxml underneath instead of string parsing.

FluentDom

FluentDOM provides a jQuery-like fluent XML interface for the DOMDocument in PHP. Selectors are written in XPath or CSS (using a CSS to XPath converter). Current versions extend the DOM implementing standard interfaces and add features from the DOM Living Standard. FluentDOM can load formats like JSON, CSV, JsonML, RabbitFish and others. Can be installed via Composer.

HtmlPageDom

Wa72HtmlPageDom is a PHP library for easy manipulation of HTML documents using DOM. It requires DomCrawler from Symfony2 components for traversing the DOM tree and extends it by adding methods for manipulating the DOM tree of HTML documents.

phpQuery

phpQuery is a server-side, chainable, CSS3 selector driven Document Object Model (DOM) API based on jQuery JavaScript Library. The library is written in PHP5 and provides additional Command Line Interface (CLI).

This is described as "abandonware and buggy: use at your own risk" but does appear to be minimally maintained.

laminas-dom

The LaminasDom component (formerly Zend_DOM) provides tools for working with DOM documents and structures. Currently, we offer LaminasDomQuery, which provides a unified interface for querying DOM documents utilizing both XPath and CSS selectors.

This package is considered feature-complete, and is now in security-only maintenance mode.

fDOMDocument

fDOMDocument extends the standard DOM to use exceptions at all occasions of errors instead of PHP warnings or notices. They also add various custom methods and shortcuts for convenience and to simplify the usage of DOM.

sabre/xml

sabre/xml is a library that wraps and extends the XMLReader and XMLWriter classes to create a simple "xml to object/array" mapping system and design pattern. Writing and reading XML is single-pass and can therefore be fast and require low memory on large xml files.

FluidXML

FluidXML is a PHP library for manipulating XML with a concise and fluent API. It leverages XPath and the fluent programming pattern to be fun and effective.

3rd-Party (not libxml-based)

The benefit of building upon DOM/libxml is that you get good performance out of the box because you are based on a native extension. However, not all 3rd-party libs go down this route. Some of them listed below

PHP Simple HTML DOM Parser

  • An HTML DOM parser written in PHP5+ lets you manipulate HTML in a very easy way!
  • Require PHP 5+.
  • Supports invalid HTML.
  • Find tags on an HTML page with selectors just like jQuery.
  • Extract contents from HTML in a single line.

I generally do not recommend this parser. The codebase is horrible and the parser itself is rather slow and memory hungry. Not all jQuery Selectors (such as child selectors) are possible. Any of the libxml based libraries should outperform this easily.

PHP Html Parser

PHPHtmlParser is a simple, flexible, html parser which allows you to select tags using any css selector, like jQuery. The goal is to assiste in the development of tools which require a quick, easy way to scrape html, whether it's valid or not! This project was original supported by sunra/php-simple-html-dom-parser but the support seems to have stopped so this project is my adaptation of his previous work.

Again, I would not recommend this parser. It is rather slow with high CPU usage. There is also no function to clear memory of created DOM objects. These problems scale particularly with nested loops. The documentation itself is inaccurate and misspelled, with no responses to fixes since 14 Apr 16.

HTML 5

You can use the above for parsing HTML5, but there can be quirks due to the markup HTML5 allows. So for HTML5 you may want to consider using a dedicated parser. Note that these are written in PHP, so suffer from slower performance and increased memory usage compared to a compiled extension in a lower-level language.

HTML5DomDocument

HTML5DOMDocument extends the native DOMDocument library. It fixes some bugs and adds some new functionality.

  • Preserves html entities (DOMDocument does not)
  • Preserves void tags (DOMDocument does not)
  • Allows inserting HTML code that moves the correct parts to their proper places (head elements are inserted in the head, body elements in the body)
  • Allows querying the DOM with CSS selectors (currently available: *, tagname, tagname#id, #id, tagname.classname, .classname, tagname.classname.classname2, .classname.classname2, tagname[attribute-selector], [attribute-selector], div, p, div p, div > p, div + p, and p ~ ul.)
  • Adds support for element->classList.
  • Adds support for element->innerHTML.
  • Adds support for element->outerHTML.

HTML5

HTML5 is a standards-compliant HTML5 parser and writer written entirely in PHP. It is stable and used in many production websites, and has well over five million downloads.

HTML5 provides the following features.

  • An HTML5 serializer
  • Support for PHP namespaces
  • Composer support
  • Event-based (SAX-like) parser
  • A DOM tree builder
  • Interoperability with QueryPath
  • Runs on PHP 5.3.0 or newer

Regular Expressions

Last and least recommended, you can extract data from HTML with regular expressions. In general using Regular Expressions on HTML is discouraged.

Most of the snippets you will find on the web to match markup are brittle. In most cases they are only working for a very particular piece of HTML. Tiny markup changes, like adding whitespace somewhere, or adding, or changing attributes in a tag, can make the RegEx fails when it's not properly written. You should know what you are doing before using RegEx on HTML.

HTML parsers already know the syntactical rules of HTML. Regular expressions have to be taught for each new RegEx you write. RegEx are fine in some cases, but it really depends on your use-case.

You can write more reliable parsers, but writing a complete and reliable custom parser with regular expressions is a waste of time when the aforementioned libraries already exist and do a much better job on this.

Also see Parsing Html The Cthulhu Way

Books

If you want to spend some money, have a look at

  • PHP Architect's Guide to Webscraping with PHP

I am not affiliated with PHP Architect or the authors.

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