Your reference points to a PHP invocation of Imagick. You should probably post your question on the Imagick forum. All the forums are at http://www.imagemagick.org/discourse-server/
With regard to the arc text and other similar effects, I wrote a command line script that does many of these kinds of text effects, (named texteffect). You can look over my script and pull out the relevant parts or use my script to do what you want in command line mode of IM. It is not implemented in PHP. So you would have to do either Anthony's or my effects by writing your own PHP code as exec commands, using Magick Wand for PHP or Imagick.
see texteffect at http://www.fmwconcepts.com/imagemagick/index.html
Note IM will soon have -distort barrel, which will allow you to do some of my "bulge and pinch" effects more efficiently.
Arced Text
Re: Arced Text
You can run Freds scripts with php see - http://www.rubblewebs.co.uk./imagemagic ... l_bash.php