I found this line a little confusing:
"May include decimal numeric character references (of the form: €) to access characters in a font beyond position 127."
I was using a font that had apostrophes and quotes stored in a non-standard position, and so they were being rendered as spaces by imagettftext. This line seemed to suggest a solution, but it took a while to figure it out.
Turns out, a "decimal numeric character reference" is a decimal conversion of the hex value of the *unicode* position of the character you want. For a while I was trying ASCII positions (I knew the ALT+ code for typing the character I needed in Windows).
In the Windows XP character map, the unicode positions are shown as U+2018 or U+201C, etc. Ignore the U+ and convert that hex number to decimal, and then stick that in your text string with the &# on the front and ; on the end, and pass it to imagettftext.
--Julian
