FilesystemPublisher will attempt to use rewrite_hash_links php which doesn't work

[ss23]

if($this->fileExtension == 'php') {
    Config::inst()->update('SSViewer', 'rewrite_hash_links', 'php');
}

This won't work because rewrite_hash_links works like:
$thisURLRelativeToBase = "<?php echo Convert::raw2att(\$_SERVER['REQUEST_URI']); >";

The static published PHP pages don't have a definition for Convert.

Simplest fix is to change Framework so that it's more like:
$thisURLRelativeToBase = "<?php echo htmlspecialchars(\$_SERVER['REQUEST_URI'], ENT_QUOTES); >";
but unsure if that's "best".

[maxime-rainville]

Need to validate if this still affects SS4.