Opentype glyphs, unicode and encoding


Hello everyone.

I'm making a PHP application to generate text labels. The PHP libraries seem to don't support OpenType features.
Now I have no problem working with unicode index to display the standard characters.
But, as far as I know, the OpenType features are name based.
For example: if I want to display a ligature «my» I have to replace «m» and «y» unicodes indexes by «my» unicode index.
The problem now is I don't have unicode indexes on this characters and I can't reffer to them by their names.

The questions are:

Is there any existing unicode for these glyphs and I am missing them?
Do I need to reencode all the glyphs?
Which is the best way to reencode a font and/or generate unicode names for this purposes?
Is there any standard?