# Saw “ Canonical HTML version: https://rocketvalidator.com/html-validation/saw-probable-cause-attempt-to-use-an-xml-processing-instruction-in-html-xml-processing-instructions-are-not-supported-in-html > Attribution: Rocket Validator (https://rocketvalidator.com) > License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) XML processing instructions are a feature of XML, not HTML. They begin with ``, and are used in XML documents to carry instructions for applications processing the document. The most common example is the XML declaration: ``. While these are perfectly valid in XML, the HTML parser does not recognize them. When the parser encounters `` processing instruction. These must be removed — only the `` element and its children should be included. **2. Unprocessed server-side code.** Languages like PHP use `` (or the short tag ``) syntax. If the server isn't configured to process PHP files, or if a `.html` file contains PHP code without being routed through the PHP interpreter, the raw `...` element. Remove the `` declaration and any other processing instructions that precede the `` tag. - **For PHP or other server-side code:** Ensure your server is properly configured to process the files. Check that the file extension matches what the server expects (e.g., `.php` for PHP files). Verify that the server-side language is installed and running. - **For other XML content:** Strip out any `` processing instructions before embedding the content in HTML. ## Examples ### ❌ Inline SVG with XML declaration ```html ``` The `` line triggers the error. ### ✅ Inline SVG without XML declaration ```html ``` ### ❌ Unprocessed PHP code in HTML output ```html

Welcome

``` If the server doesn't process the PHP, the raw `` ends up in the HTML and triggers this error. ### ✅ Properly processed output (or static HTML equivalent) ```html

Welcome

Hello, World!

``` ### ❌ SVG with an XML stylesheet processing instruction ```html ``` ### ✅ SVG without the processing instruction ```html ``` In HTML, use standard `` or `