wp-includes/SimplePie/src/Parser.php:658$datastring private static function set_doctype(string $data): string { // Strip DOCTYPE except if containing an [internal subset] $data = preg_replace('/^\\s*<!DOCTYPE\\s[^>\\[\\]]*>\s*/', '', $data) ?? $data; // Declare HTML entities only if no remaining DOCTYPE $doctype = preg_match('/^\\s*<!DOCTYPE\\s/', $data) ? '' : self::declare_html_entities(); return $doctype . $data; }Unchanged from 6.9.7 through 7.1.0.
Signature, return type and hooks compared across 3 parsed releases.
src/wp-includes/SimplePie/src/Parser.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.