Code highlighting color issue for PHP for function named "fn"

[roblourens]

From microsoft/vscode#105742

<?

function fn(){
	// do something
};

?>
<div><?=fn()?></div>

[KapitanOczywisty]

@ottopic @roblourens It's reserved since PHP 7.4 https://3v4l.org/T4SHV

Docs:
https://www.php.net/manual/en/functions.arrow.php
https://www.php.net/manual/en/reserved.keywords.php

[sadick254]

Closing this for now based on the #401 (comment) and the PHP docs pointed to.