From a readability POV it might make sense to move the "preface" one level up - and - to remove the additional, second "manual" level all together.
Stated differently - Current outline:
* Copyright
* https://www.php.net/manual/en/copyright.php
* PHP Manual
* https://www.php.net/manual/en/manual.php
* Getting Started
* https://www.php.net/manual/en/getting-started.php
* ...
Proposed outline improvement:
* Copyright
* https://www.php.net/manual/en/copyright.php
* Preface
* https://www.php.net/manual/en/preface.php
* Getting Started
* https://www.php.net/manual/en/getting-started.php
* ...