How to Safely Perform preg_replace on HTML Without Breaking Tags?

Ignoring HTML Tags in preg_replace Patterns

When performing text replacement using preg_replace, it's essential to handle HTML tags properly to avoid breaking the structure of the HTML document. Ignoring tags ensures that substitutions are not applied within tag boundaries.

Why Use DOMDocument and DOMXPath?

While regular expressions can be powerful, parsing HTML with them is often problematic. Instead, consider using DOMDocument and DOMXPath. These tools allow you to navigate and manipulate HTML documents as a tree structure, providing a robust solution for ignoring HTML tags in the context of preg_replace.

Utilizing XPath for Precise Search

XPath allows you to locate specific elements or text nodes within an HTML document. By leveraging XPath, you can query for text nodes that contain the search term but exclude nodes within HTML tags. This ensures that the replacement pattern is not applied to HTML content.

Creating TextRanges for Node Modification

Once you have identified the text nodes that match the search term, it's necessary to wrap them in the desired span tag. To facilitate this, consider creating a TextRange class that represents a list of DOMText nodes. This allows you to perform string operations on the text nodes as if they were a single string.

Replacing and Wrapping Text with Spans

By iterating through the selected text nodes, you can use replaceChild() to insert a span tag around each node. This wraps the matching text in the span tag without affecting the HTML tags.

Limitations and Notes

It's important to note that this approach relies on binary string search and offsets, which can lead to inaccuracies in UTF-8 encoded content. To ensure correct operation, consider using mb_strpos to obtain the UTF-8 character offset when searching for the search term.

The code example in the answer provides a complete solution for ignoring HTML tags in a preg_replace pattern, allowing you to perform text substitutions without compromising the integrity of the HTML document.

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