Use the following to decode all entities:
<?php html_entity_decode($string, ENT_QUOTES | ENT_XML1, 'UTF-8') ?>
I've checked these special entities:
- double quotes (")
- single quotes (' and ')
- non printable chars (e.g. )
With other $flags some or all won't be decoded.
It seems that ENT_XML1 and ENT_XHTML are identical when decoding.