Is it Effective to Use Regexp for Manipulating XML Documents?-PHP Tutorial-php.cn

Is it Effective to Use Regexp for Manipulating XML Documents?

Mary-Kate Olsen

Release： 2024-10-20 16:00:03

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Is it Effective to Use Regexp for Manipulating XML Documents?

Adding Attributes to XML Tags with Regexp

XML documents are structured and well-formed data that cannot be adequately parsed using regular expressions. It is essential to leverage XML-specific tools and libraries to modify XML data effectively.

Avoid Regexp for XML Manipulation

Using regular expressions to manipulate XML documents is highly discouraged. XML is not a regular language, and regex patterns are insufficient to navigate its complex structure.

Use XML Extensions

Instead, it is recommended to use the XML extensions of PHP to modify XML documents. Consider the following example:

<code class="php">$xml = new SimpleXml(file_get_contents($xmlFile));

function process_recursive($xmlNode) {
    $xmlNode->addAttribute('attr', 'myAttr');
    foreach ($xmlNode->children() as $childNode) {
        process_recursive($childNode);
    }
}

process_recursive($xml);
echo $xml->asXML();</code>

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This code uses the SimpleXml class to load the XML document. The process_recursive function then traverses the XML tree, adding the desired attribute to each node. Finally, the modified XML is printed using asXML.

Limitations of Regexp

Regular expressions fail to handle complex XML structures, such as:

<code class="xml"><?xml version="1.0" encoding='UTF-8'?>
<html>
    <head>
        <!-- <meta> ... </meta> -->
        <script>//<![CDATA[
            function load() {document.write('<tt>Test</tt>');}
        //]]></script>
        <title><![CDATA[Fancy <<SiteName>> [with Breadcrumbs] > in > title]]></title>
    </head>
    <body onload="load()">
        <input
            type="submit"
            value="multiline
                   button
                   text"
        />
    </body>
</html></code>

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Regex patterns are unable to correctly process these elements, resulting in invalid XML.

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