Problems with some characters

I was having problems with this character: ’

It displays as some rhombus like gibberish.

To fix this, I added $content =mb_convert_encoding($content,'UTF-8'); before displaying.

Now it doesn’t display the gibberish and the character ’ either.

How do I fix this?

1. Make sure to set the page charset to UTF-8 in the header
2. If you write these signs in the document itself, make sure to save it as UTF-8
3. If you store them in a database, make sure to have the table charset set to UTF-8 and write to and read from the database with the same charset.