Hello.
I created a project on PHP 7.4 using the PHP Tools 1.50.12639 (note that that VS is updating the tool on it's own).
Now the coloring of the code and so on is not working once it reaches code with short PHP tags.
I can confirm that the smarty files are affected too, especially the JS code inside, in which case you see pieces underlined with red, making you think that you have errors in your code, but there is no error in reality.