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Example of parsing and processing HTML/XML using SAX in PHP

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Release： 2023-09-08 09:00:02

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Example of parsing and processing HTML/XML using SAX in PHP

Example of using SAX to parse and process HTML/XML in PHP

Overview:
SAX (Simple API for XML) is a streaming, Event-driven XML parsing method. It processes XML documents in a low-overhead way and is suitable for large XML files. In PHP, we can use SAX parser to parse and process HTML/XML documents. This article will introduce examples of how to use SAX to parse and process HTML/XML documents in PHP.

Example:
Consider the following HTML document as our example:

<html>
<body>
    <h1>Welcome to SAX Parsing</h1>
    <p>This is a paragraph.</p>
    <ul>
        <li>Item 1</li>
        <li>Item 2</li>
        <li>Item 3</li>
    </ul>
</body>
</html>

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Our goal is to use a SAX parser to extract and print out the contents of the HTML document. To achieve this, we will create a class that inherits from PHP's SAX handler interface DefaultHandler and override some of its methods to handle events. The following is the sample code:

// 导入PHP的SAX处理类
require_once "XML/SaxParser.php";

// 创建一个继承自DefaultHandler的类
class MySaxHandler extends XML_SaxParser_DefaultHandler {
    private $currentTag = "";

    // 处理元素开始事件
    public function startElement($name, $attrs) {
        $this->currentTag = $name;
    }

    // 处理元素结束事件
    public function endElement($name) {
        // 清空当前标签
        $this->currentTag = "";
    }

    // 处理元素内容事件
    public function characters($data) {
        // 如果当前标签不为空，则打印出内容
        if (!empty($this->currentTag)) {
            echo "Tag: " . $this->currentTag . " - " . $data . PHP_EOL;
        }
    }
}

// 创建一个SAX解析器实例
$saxParser = new XML_SaxParser();

// 创建一个自定义的SAX处理器实例
$mySaxHandler = new MySaxHandler();

// 将SAX处理器实例设置给SAX解析器
$saxParser->setHandler($mySaxHandler);

// 解析HTML文档
$saxParser->parseFile("example.html");

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Output:

Tag: h1 - Welcome to SAX Parsing
Tag: p - This is a paragraph.
Tag: li - Item 1
Tag: li - Item 2
Tag: li - Item 3

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Through the above example, we created a custom SAX handler class MySaxHandler to handle element start, element end, and element content events. In the startElement method, we record the name of the current label; in the endElement method, we clear the value of the current label; in the characters method, we print out the non-empty label and its content.

Then, we created a SAX parser instance $saxParser and a custom SAX processor instance $mySaxHandler, and set the latter to the former. Finally, we use the parseFile method of $saxParser to parse the HTML document.

Conclusion:
SAX is an efficient way to parse and process XML/HTML documents. In PHP, we can use SAX parser to parse, process and extract the content of XML/HTML documents. By creating a class that inherits from DefaultHandler and overriding its methods, we can customize the handler to handle different types of events. This article gives a basic example, hoping to help readers quickly get started and understand how to use SAX to parse and process HTML/XML documents in PHP.

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