aspell works only with very old (up to .27.* or
so) versions of aspell library. Neither this module,
nor those versions of aspell library are supported any
longer. If you want to use spell-checking capabilities
in PHP, use pspell
instead. It uses pspell library and works with newer
versions of aspell.
You need the aspell library, available from:
http://aspell.sourceforge.net/.
See also pspell.