How can PHP be used to generate XHTML documents with embedded SVG code?

To generate XHTML documents with embedded SVG code using PHP, you can use the `echo` function to output the required XHTML and SVG code. You can also use PHP variables to dynamically generate SVG content based on user input or other data sources.

<?php
header("Content-type: application/xhtml+xml");
echo '<?xml version="1.0" encoding="UTF-8"?>';
echo '<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">';
echo '<html xmlns="http://www.w3.org/1999/xhtml">';
echo '<head><title>Embedded SVG Example</title></head>';
echo '<body>';
echo '<svg width="100" height="100">';
echo '<circle cx="50" cy="50" r="40" stroke="black" stroke-width="3" fill="red" />';
echo '</svg>';
echo '</body>';
echo '</html>';
?>