<?php
ini_set('display_errors', 1);
$d = new DOMDocument();
$html = "<!DOCTYPE html><html><head><meta charset='UTF-8'><title>a title with a \x0</title></head><body>U+0000 <span>\x0</span></body></html>";
$d->loadHTML($html);
print($d->saveHTML());
Warning: DOMDocument::loadHTML(): Char 0x0 out of allowed range in Entity, line: 1 in /in/pTGEr on line 6
<!DOCTYPE html>
<html><head><meta charset="UTF-8"><title>a title with a </title></head><body>U+0000 <span></span></body></html>