wp-includes/html-api/class-wp-html-processor.php:888Indicates if the currently-matched token is virtual, created by a stack operation while processing HTML, rather than a token found in the HTML text itself.
bool private function is_virtual(): bool { return ( isset( $this->current_element->provenance ) && 'virtual' === $this->current_element->provenance ); }Introduced in 6.6.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/html-api/class-wp-html-processor.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.